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DNA, the molecular basis for inheritance.
^ We suggest that the tight binding of RC to lambda DNA is due to interaction of RC with other DNA-bound proteins, and is related to the molecular basis of the lambda cro- plasmid replication control.

Each strand of DNA is a chain of nucleotides, matching each other in the center to form what look like rungs on a twisted ladder.
.Genetics (from Ancient Greek γενετικός genetikos, “genitive” and that from γένεσις genesis, “origin”[1][2][3]), a discipline of biology, is the science of heredity and variation in living organisms.^ The word "gene" is shared by many disciplines, including classical genetics, molecular genetics, evolutionary biology and population genetics.

^ Nearly all living things use the same genetic code, called the standard genetic code, although a few organisms use minor variations of the standard code.

^ Closely-related fields The science which grew out of the union of biochemistry and genetics is widely known as molecular biology.

[4][5] .The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding.^ Humans began applying knowledge of genetics in prehistory with the domestication and breeding of plants and animals.

^ History The existence of genes was first suggested by Gregor Mendel, who studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring.

^ Just how the presence of specific features in the molecular structure of chromosomes could produce traits and behaviors in living organisms was unimaginable at the time.

.However, the modern science of genetics, which seeks to understand the process of inheritance, only began with the work of Gregor Mendel in the mid-nineteenth century.^ For a breeder or any person interested in inheritance, you only need to understand Mendelian genetics (also called "Classical" or "Transmission" genetics).

^ For the process to work, genetic distance must be measured by linkage and association, but the accuracy of these measurements depends on the accuracy of the genetic model and disease phenotype.
  • Genetics 14 January 2010 4:14 UTC www.acnp.org [Source type: Academic]

^ Weber (2005), however, seeks to replace Nagel's conception with one that retains the idea that reductive explanation involves subsumption under laws of the reducing science.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

[6] .Although he did not know the physical basis for heredity, Mendel observed that organisms inherit traits via discrete units of inheritance, which are now called genes.^ Each inherited trait of a person is encoded by genes.

^ Mendel was unaware of the physical nature of the gene.

^ Physical changes in genes are called mutations .

.Genes correspond to regions within DNA, a molecule composed of a chain of four different types of nucleotides—the sequence of these nucleotides is the genetic information organisms inherit.^ These consist of pairs of four types of molecules which are called bases.

^ These four nucleotides constitute the genetic alphabet.

^ The genetic information carried by an organism - its genome - is inscribed in a DNA molecule.

.DNA naturally occurs in a double stranded form, with nucleotides on each strand complementary to each other.^ The polymerase catalyzes the sequence-specific incorporation of fluorescent nucleotides into nascent complementary strands on all the templates.

^ When the process is complete, two copies of the original double helix have been formed and hence the genes in the original DNA molecule have been effectively replicated.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The A form appears likely to occur only in dehydrated samples of DNA, such those used in crystallography experiments, and possibly in hybrid pairings of DNA and RNA strands.

.Each strand can act as a template for creating a new partner strand—this is the physical method for making copies of genes that can be inherited.^ Applications of plasmids Plasmids serve as important tools in genetics and biochemistry labs, where they are commonly used to multiply (make many copies of) or express particular genes.

^ Can genes make one person more likely to act violently than another?
  • Genetics | Science and Technology News, Stories | Discover Magazine 14 January 2010 4:14 UTC discovermagazine.com [Source type: FILTERED WITH BAYES]

^ The same strengths of the method will make it far easier to positionally clone genes once linkages are found.
  • Genetics 14 January 2010 4:14 UTC www.acnp.org [Source type: Academic]

.The sequence of nucleotides in a gene is translated by cells to produce a chain of amino acids, creating proteins—the order of amino acids in a protein corresponds to the order of nucleotides in the gene.^ So, this RNA sequence represents a protein sequence, three amino acids long.

^ The sequence of codons in a gene specifies the amino-acid sequence of the protein it encodes.

^ The relationship between the nucleotide sequence and the amino-acid sequence of the protein is determined by simple cellular rules of translation, known collectively as the genetic code.

.This relationship between nucleotide sequence and amino acid sequence is known as the genetic code.^ The relationship between the nucleotide sequence and the amino-acid sequence of the protein is determined by simple cellular rules of translation, known collectively as the genetic code.

^ The genetic code determines the sequence of the amino acids that make up a protein.

^ These variable codes for amino acids are possible because of modified bases in the first base of the anticodon, and the basepair formed is called a wobble base pair.

.The amino acids in a protein determine how it folds into a three-dimensional shape; this structure is, in turn, responsible for the protein's function.^ So, this RNA sequence represents a protein sequence, three amino acids long.

^ The polypeptide is ultimately folded into a 3-dimensional protein structure, which will go on to perform some specific function in the cell such as an enzyme subunit or cell membrane component.

^ Because protein complexes are responsible for most biological functions, genetic interactions are a powerful tool.

.Proteins carry out almost all the functions needed for cells to live.^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

^ Each human carries six to eight abnormal recessive genes but these genes do not cause cells to function abnormally except when two similar recessive genes are present.

^ Genetics is the study of what make up an animals or plants.DNA carries all the information needed for protein synthesis and replication of cells.

.A change to the DNA in a gene can change a protein's amino acids, changing its shape and function: this can have a dramatic effect in the cell and on the organism as a whole.^ The sequence of codons in a gene specifies the amino-acid sequence of the protein it encodes.

^ However, there is another allele for this gene that has one different nitrogenous base in its DNA sequence, and thus, one codon in the middle of the gene codes for a different amino acid in an important place in the hemoglobin molecule.
  • Genetics Practice Problems 14 January 2010 4:14 UTC www.biology.clc.uc.edu [Source type: FILTERED WITH BAYES]

^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

.Although genetics plays a large role in the appearance and behavior of organisms, it is the combination of genetics with what an organism experiences that determines the ultimate outcome.^ Nearly all living things use the same genetic code, called the standard genetic code, although a few organisms use minor variations of the standard code.

^ Although the sequence has been determined, the actual specific functions of most of the genetic code remain unknown.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ If a gene is beneficial, natural selection is likely to be the major determinant of its equilibrium frequency; the rate of sporadic mutation to that gene will play at most a minor role.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.For example, while genes play a role in determining an organism's size, the nutrition and other conditions it experiences after inception also have a large effect.^ Our current studies examine the role played by NOS1AP, also termed CAPON, a gene linked to schizophrenia in regulating dendrite morphology.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ These studies indicate that the small subunit of the oxygenase is essential for activity but does not play a major role in determining the specificity of these enzymes.

^ In addition, gene networks are identified that may play a role in the pathophysiology of autism.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

Contents

History

Morgan's observation of sex-linked inheritance of a mutation causing white eyes in Drosophila led him to the hypothesis that genes are located upon chromosomes.
.Although the science of genetics began with the applied and theoretical work of Gregor Mendel in the mid-1800s, other theories of inheritance preceded Mendel.^ Gregor Mendel (1822 1884) was an Augustinian monk who conducted very extensive crossbreeding experiments with peas and other plants.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ Although the philosophical case for anti-reductionism has been challenged, many philosophers still assume that the anti-reductionist account of genetics provides an exemplar for anti-reductionist analyses of other sciences.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The special problems of applying molecular strategies to complex traits can be appreciated with an understanding of the genetic epidemiology of mental disorders and the theoretical underpinnings of the molecular genetic strategies.
  • Genetics 14 January 2010 4:14 UTC www.acnp.org [Source type: Academic]

.A popular theory during Mendel's time was the concept of blending inheritance: the idea that individuals inherit a smooth blend of traits from their parents.^ The key ideas behind Mendel's theory of inheritance are straightforward.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ History The existence of genes was first suggested by Gregor Mendel, who studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring.

^ He constructs a new concept of reductive explanation based on his own idea of what effectively constitutes a scientific theory and his unificationist account of scientific explanation (1989).
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.Mendel's work disproved this, showing that traits are composed of combinations of distinct genes rather than a continuous blend.^ But this account shows that genes and DNA play a distinctive causal role in that genes are the causally specific actual difference makers of difference in the linear sequences of unprocessed RNA molecules.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The traits a puppy shows and carries for each gene series is determined by the two alleles they inherited.
  • Dachshund Puppies by Li'l Dachs - Li'l Dachs Genetics 14 January 2010 4:14 UTC www.lildachs.com [Source type: FILTERED WITH BAYES]

^ Some traits, some phenotypes, are controlled by more than one gene.
  • Genetics Practice Problems 14 January 2010 4:14 UTC www.biology.clc.uc.edu [Source type: FILTERED WITH BAYES]

.Another theory that had some support at that time was the inheritance of acquired characteristics: the belief that individuals inherit traits strengthened by their parents.^ The observation that some genes do not segregate independently at meiosis, broke the laws of Mendelian inheritance, and provided science with a way to map characteristics to a location on the chromosomes.

^ History The existence of genes was first suggested by Gregor Mendel, who studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring.

.This theory (commonly associated with Jean-Baptiste Lamarck) is now known to be wrong—the experiences of individuals do not affect the genes they pass to their children.^ Applications of plasmids Plasmids serve as important tools in genetics and biochemistry labs, where they are commonly used to multiply (make many copies of) or express particular genes.

^ In what is now known as Griffith's experiment, injections into a mouse of a deadly strain of a bacteria that had been heat-killed transferred genetic information to a safe strain of the same bacteria, killing the mouse.

^ Neither genome screens of affected siblings nor the large number of association studies using candidate genes have resulted in finding autism susceptibility genes.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

[7] Other theories included the pangenesis of Charles Darwin (which had both acquired and inherited aspects) and Francis Galton's reformulation of pangenesis as both particulate and inherited.[8]

Mendelian and classical genetics

.The modern science of genetics traces its roots to Gregor Johann Mendel, a German-Czech Augustinian monk and scientist who studied the nature of inheritance in plants.^ History The existence of genes was first suggested by Gregor Mendel, who studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring.

^ History It was not until 1865 that Gregor Mendel first traced inheritance patterns of certain traits in pea plants and showed that they obeyed simple statistical rules.

^ Studying genetic interactions can reveal gene function, the nature of the mutations, functional redundancy, and protein interactions.

.In his paper "Versuche über Pflanzenhybriden" ("Experiments on Plant Hybridization"), presented in 1865 to the Naturforschender Verein (Society for Research in Nature) in Brünn, Mendel traced the inheritance patterns of certain traits in pea plants and described them mathematically.^ History It was not until 1865 that Gregor Mendel first traced inheritance patterns of certain traits in pea plants and showed that they obeyed simple statistical rules.

^ Gregor Mendel's paper, Experiments on Plant Hybridization .

^ In this way, early geneticists were able to trace inheritance patterns without any knowledge whatsoever of molecular biology.

[9] .Although this pattern of inheritance could only be observed for a few traits, Mendel's work suggested that heredity was particulate, not acquired, and that the inheritance patterns of many traits could be explained through simple rules and ratios.^ DNA is sometimes referred to as the molecule of heredity as it is inherited and used to propagate traits.

^ The selection of a trait that was represented in variations could take a relatively few generations.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ History The existence of genes was first suggested by Gregor Mendel, who studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring.

.The importance of Mendel's work did not gain wide understanding until the 1890s, after his death, when other scientists working on similar problems re-discovered his research.^ The significance of Mendel's work was not understood until early in the twentieth century, after his death, when his research was re-discovered by other scientists working on similar problems.

^ However, the regulation of emotional responsiveness to social cues lies at the heart of the problem, and recent research indicates that we may be nearing a deeper and more comprehensive understanding.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ In the early 1900s, Mendel's work received renewed attention from scientists.

William Bateson, a proponent of Mendel's work, coined the word genetics in 1905.[10][11] (The adjective genetic, derived from the Greek word genesisγένεσις, "origin" and that from the word gennoγεννώ, "to give birth", predates the noun and was first used in a biological sense in 1860.)[12] Bateson popularized the usage of the word genetics to describe the study of inheritance in his inaugural address to the Third International Conference on Plant Hybridization in London, England, in 1906.[13]
.After the rediscovery of Mendel's work, scientists tried to determine which molecules in the cell were responsible for inheritance.^ A variety of data implicate the presence, on the apoptotic cell surface, of specific evolutionarily conserved recognition determinants that elicit innate anti-inflammatory responses.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ The significance of Mendel's work was not understood until early in the twentieth century, after his death, when his research was re-discovered by other scientists working on similar problems.

^ The rediscovery of Mendel's work in 1900 did not lead the scientific community to be converted to Mendelism overnight.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.In 1910, Thomas Hunt Morgan argued that genes are on chromosomes, based on observations of a sex-linked white eye mutation in fruit flies.^ In 1910, Thomas Hunt Morgan proved that chromosomes are the carriers of genes.

^ Thomas Hunt Morgan shows that genes reside on chromosomes .

^ The genes on the X chromosome are called sex-linked or X- linked genes.

[14] .In 1913, his student Alfred Sturtevant used the phenomenon of genetic linkage to show that genes are arranged linearly on the chromosome.^ Gene maps show chromosomes containing linear arranged genes .

^ Applications of plasmids Plasmids serve as important tools in genetics and biochemistry labs, where they are commonly used to multiply (make many copies of) or express particular genes.

^ Nonetheless, mounting evidence for genetic linkage of autism to the chromosome 17q11.2 region that harbors the SERT locus (SLC6A4) supports a genetic effect at or near this gene.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

[15]

Molecular genetics

.Although genes were known to exist on chromosomes, chromosomes are composed of both protein and DNA—scientists did not know which of these is responsible for inheritance.^ As BRCA1 -/- tumors have characteristic abnormalities in DNA repair, and in maintenance of X chromosome inactivation, we explored these parameters in sporadic basal-like breast cancers.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ But in many cases, genes on the same chromosome that are inherited together produce offspring with unexpected allele combinations.

^ DNA strand may also be silenced through DNA methylation or by chemical changes to the protein components of chromosomes (see histone).

.In 1928, Frederick Griffith discovered the phenomenon of transformation (see Griffith's experiment): dead bacteria could transfer genetic material to "transform" other still-living bacteria.^ Frederick Griffith discovers a hereditary molecule that is transmissible between bacteria (see Griffiths experiment) .

^ In 1928, Frederick Griffith showed that genes could be transferred.

^ In what is now known as Griffith's experiment, injections into a mouse of a deadly strain of a bacteria that had been heat-killed transferred genetic information to a safe strain of the same bacteria, killing the mouse.

.Sixteen years later, in 1944, Oswald Theodore Avery, Colin McLeod and Maclyn McCarty identified the molecule responsible for transformation as DNA.^ Oswald Avery, Collin Macleod, and Maclyn McCarty showed in 1944 that DNA holds the gene's information.

^ Oswald Theodore Avery, Colin McLeod and Maclyn McCarty isolate DNA as the genetic material (at that time called transforming principle) .

[16] .The Hershey-Chase experiment in 1952 also showed that DNA (rather than protein) is the genetic material of the viruses that infect bacteria, providing further evidence that DNA is the molecule responsible for inheritance.^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

^ DNA is sometimes referred to as the molecule of heredity as it is inherited and used to propagate traits.

^ Edward Lawrie Tatum and George Wells Beadle show that genes code for proteins; see the original central dogma of genetics .

[17]
.James D. Watson and Francis Crick determined the structure of DNA in 1953, using the X-ray crystallography work of Rosalind Franklin and Maurice Wilkins that indicated DNA had a helical structure (i.e., shaped like a corkscrew).^ DNA structure is resolved to be a double helix by James D. Watson and Francis Crick .

^ In 1953, James D. Watson and Francis Crick demonstrated the molecular structure of DNA. Together, these discoveries established the central dogma of molecular biology, which states that proteins are transcribed from RNA which is translated from DNA. This dogma has since been shown to have exceptions, such as reverse transcription in retroviruses.

^ Francis Crick, James D. Watson, Maurice Wilkins, Rosalind Franklin, Seymour Benzer, et al., took up the physicist's challenge to work out the structure of the chromosomes and the question of how the segments of the chromosomes that were conceived to relate to specific traits could possibly do their jobs.

[18][19] .Their double-helix model had two strands of DNA with the nucleotides pointing inward, each matching a complementary nucleotide on the other strand to form what looks like rungs on a twisted ladder.^ The pair of nucleotide chains in a DNA molecule twist around one another in the form of a double helix.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ In a DNA double helix, two polynucleotide strands can associate through the hydrophobic effect.

^ The polymerase catalyzes the sequence-specific incorporation of fluorescent nucleotides into nascent complementary strands on all the templates.

[20] .This structure showed that genetic information exists in the sequence of nucleotides on each strand of DNA. The structure also suggested a simple method for duplication: if the strands are separated, new partner strands can be reconstructed for each based on the sequence of the old strand.^ In the genetic code, occasionally sequences are duplicated.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ (This is the entire sequence of one DNA strand.

^ The concept of genetic information has a prominent place in the history of molecular genetics, beginning with Watson and Crick's observation that since any sequence of nucleotide base pairs could fit into the structure of any DNA molecule “that in a long molecule many different permutations are possible, and it therefore seems likely that the precise sequence of the bases is the code which carries the genetic information.” (Watson and Crick 1953).
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.Although the structure of DNA showed how inheritance works, it was still not known how DNA influences the behavior of cells.^ Although not all features show these patterns of Mendelian inheritance, his work acted as a proof that application of statistics to inheritance could be highly useful.

^ The present study shows that an extensive, structured work up yields a diagnosis in at least 20%, and possibly up to 36% of adult autistic subjects with mental retardation.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ The discovery of DNA and the double helix Working in the 19th century, biochemists initially isolated DNA and RNA (mixed together) from cell nuclei.

.In the following years, scientists tried to understand how DNA controls the process of protein production.^ Once mRNA has been transcribed from DNA, it is exported from the nucleus into the cytoplasm (in eukaryotes mRNA is "processed" before being exported), where it is bound to ribosomes and translated into protein.

^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

^ This plasmid may have special promoter elements to drive production of the protein of interest, and may also have antibiotic resistance markers to help follow the plasmid.

.It was discovered that the cell uses DNA as a template to create matching messenger RNA (a molecule with nucleotides, very similar to DNA).^ These messenger RNAs are used as templates by the cell machinery that produces the proper protein molecules.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ Synthesis RNA is made by an enzyme, RNA polymerase, using DNA as a template.

^ DNA is sometimes referred to as the molecule of heredity as it is inherited and used to propagate traits.

.The nucleotide sequence of a messenger RNA is used to create an amino acid sequence in protein; this translation between nucleotide and amino acid sequences is known as the genetic code.^ In the genetic code, occasionally sequences are duplicated.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ These codons can then be translated with messenger RNA and then transfer RNA, with a codon corresponding to a particular amino acid.

^ The sequence of codons in a gene specifies the amino-acid sequence of the protein it encodes.

With this molecular understanding of inheritance, an explosion of research became possible. .One important development was chain-termination DNA sequencing in 1977 by Frederick Sanger: This technology allows scientists to read the nucleotide sequence of a DNA molecule.^ The polymerase chain reaction is an extremely versatile technique for copying DNA. In brief, PCR allows a single DNA sequence to be copied (millions of times), or altered in predetermined ways.

^ In genetics terminology, sequencing is most often restricted to determining the nucleotides of a DNA or RNA strand.

^ Every plasmid contains at least one DNA sequence that serves as an origin of replication or ori (a starting point for DNA replication), which enables the plasmid DNA to be duplicated independently from the chromosomal DNA. .

[21] .In 1983, Kary Banks Mullis developed the polymerase chain reaction, providing a quick way to isolate and amplify a specific section of a DNA from a mixture.^ The polymerase chain reaction is an extremely versatile technique for copying DNA. In brief, PCR allows a single DNA sequence to be copied (millions of times), or altered in predetermined ways.

^ Polymerase chain reaction (PCR) Main article: Polymerase chain reaction .

[22] Through the pooled efforts of the Human Genome Project and the parallel private effort by Celera Genomics, these and other techniques culminated in the sequencing of the human genome in 2003.[23]

Features of inheritance

Discrete inheritance and Mendel's laws

A Punnett square depicting a cross between two pea plants heterozygous for purple (B) and white (b) blossoms
.At its most fundamental level, inheritance in organisms occurs by means of discrete traits, called genes.^ Each inherited trait of a person is encoded by genes.

^ A gene's most common allele is called the wild type allele, and rare alleles are called mutants.

^ The gene, tracked to chromosome seven, is a dominant gene, meaning that people only have to inherit one copy to be affected.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

[24] .This property was first observed by Gregor Mendel, who studied the segregation of heritable traits in pea plants.^ History The existence of genes was first suggested by Gregor Mendel, who studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring.

^ History It was not until 1865 that Gregor Mendel first traced inheritance patterns of certain traits in pea plants and showed that they obeyed simple statistical rules.

^ Overall, we were not able to replicate the findings of the first study on 5-HTT and autism and instead observed a tendency for association of the opposite genetic variant of the gene with the disorder.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

[9][25] .In his experiments studying the trait for flower color, Mendel observed that the flowers of each pea plant were either purple or white – and never an intermediate between the two colors.^ Codominant "blue" and "purple" alleles would result in color blending and hence, violet flower petals.

^ For example, in the case of blossom color, if the "red" allele is dominant to the "white" allele, in a heterozygous flower (with one red and one white allele), the petals will be red.

^ A purebred tall, red flowered, large seeded plant is crossed the a purebred short white flowered, small seeded plant.

.These different, discrete versions of the same gene are called alleles.^ The different forms of the genes are known as alleles.

^ Geneticists call these split genes .
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The group of alleles of these genes that is passed as a unit is called: .

.In the case of pea, which is a diploid species, each individual plant has two alleles of each gene, one allele inherited from each parent.^ Sexually reproducing species have somatic cells (body cells), which are diploid [2n] (they have two sets of chromosomes, one from the mother, one from the father) or polyploid [Xn] (more than two sets of chromosomes), and gametes (reproductive cells) which are haploid [n] (they have only one set of chromosomes).

^ Two genes positioned near one another on a chromosome may encode proteins that figure in the same cellular process or in completely unrelated processes.

^ Genes that appear together on the chromosomes of one species, such as humans, may appear on separate chromosomes in another species, such as mice.

[26] .Many species, including humans, have this pattern of inheritance.^ I will describe the first mammalian model system to mimic several hallmarks of human nondisjunction, including altered recombination patterns.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ Like many sexually reproducing species, humans have special gonosomes (sex chromosomes, in contrast to autosomes for body functions).

.Diploid organisms with two copies of the same allele of a given gene are called homozygous at that gene locus, while organisms with two different alleles of a given gene are called heterozygous.^ The different forms of the genes are known as alleles.

^ An organism in which both copies of the gene are identical - that is, have the same allele - is said to be homozygous for that gene.

^ Typically, an organism can pass on a allele without regard to which allele was passed on for a different gene.

.The set of alleles for a given organism is called its genotype, while the observable traits of the organism are called its phenotype.^ If there is little plasticity, the phenotype of an organism can be reliably predicted from knowledge of the genotype, regardless of environmental peculiarities during development.

^ The phenotype of an individual organism is either its total physical appearance and constitution, or a specific manifestation of a trait, such as size or eye color, that varies between individuals.

^ The genotype of an organism represents its exact genetic makeup, that is, the particular set of genes it possesses.

.When organisms are heterozygous at a gene, often one allele is called dominant as its qualities dominate the phenotype of the organism, while the other allele is called recessive as its qualities recede and are not observed.^ Often one allele is "dominant" and the other is "recessive" - the "dominant" allele will determine what trait is expressed.

^ An organism which has two different alleles of the gene is said to be heterozygous.

^ It is not uncommon for a person to have abnormalities of one or more gene and especially the recessive genes.

.Some alleles do not have complete dominance and instead have incomplete dominance by expressing an intermediate phenotype, or codominance by expressing both alleles at once.^ Color locus: "red" allele and "white" allele show incomplete dominance.

^ E.      The allele causing short coat and the allele causing shaggy coat show incomplete dominance.

^ Some genes only express a given phenotype in certain environmental conditions.

[27]
.When a pair of organisms reproduce sexually, their offspring randomly inherit one of the two alleles from each parent.^ When organisms reproduce the offspring tend to resemble their parents.

^ A plant inherits one factor from each of its parents.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ If you inherited one gene from one parent, you would have to also inherit the other gene from that same parent.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

.These observations of discrete inheritance and the segregation of alleles are collectively known as Mendel's first law or the Law of Segregation.^ Equation (1) is known as a ‘recurrence’ equation—it expresses the frequency of the A 1 allele in the second generation in terms of its frequency in the first generation.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The observation that some genes do not segregate independently at meiosis, broke the laws of Mendelian inheritance, and provided science with a way to map characteristics to a location on the chromosomes.

^ These pairs of genes, which are located locus to locus, are known as alleles (think of allies).
  • Genetics 14 January 2010 4:14 UTC www.lovebirds.ca [Source type: FILTERED WITH BAYES]

Notation and diagrams

Genetic pedigree charts help track the inheritance patterns of traits.
.Geneticists use diagrams and symbols to describe inheritance.^ The differences used by classical geneticists to explain inheritance patterns have been routinely identified at the molecular level by contemporary geneticists.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ Using this genetic distance principal and mind numbingly tedious inheritance studies, geneticists have been able to determine the approximate physical chromosome location of many genetic disease genes.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

.A gene is represented by a letter (or letters)—the capitalized letter represents the dominant allele and the recessive is represented by lowercase.^ Twenty percent of males with the fragile site are unaffected, and conversely, 30% of female heterozygotes are mildly affected, so the gene is neither completely dominant nor fully recessive.
  • Genetics 14 January 2010 4:14 UTC www.acnp.org [Source type: Academic]

^ Autosomal Dominant : A dominant gene will always express itself regardless of whether its paired allele gene is the same or has been altered.
  • Genetics 14 January 2010 4:14 UTC www.lovebirds.ca [Source type: FILTERED WITH BAYES]

^ The ways that gene copies interact are explained by chemical dominance relationships (more at genetics, allele).

[28] .Often a "+" symbol is used to mark the usual, non-mutant allele for a gene.^ The genetic symbols are used to identify the different mutant genes from their non-mutant or wild form genes.
  • Genetics 14 January 2010 4:14 UTC www.lovebirds.ca [Source type: FILTERED WITH BAYES]

^ When this principle is used to explain an actual hereditary pattern, it is applied to genes that actually differed in the population exhibiting the pattern (often an experimental population).
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ A gene's most common allele is called the wild type allele, and rare alleles are called mutants.

[citation needed]
.In fertilization and breeding experiments (and especially when discussing Mendel's laws) the parents are referred to as the "P" generation and the offspring as the "F1" (first filial) generation.^ Breeding experiments and heredity studies are generally confined to exploring variation and natural selection.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ History The existence of genes was first suggested by Gregor Mendel, who studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring.

^ He then crossed these to produce the first daughter generation (the F1 generation).
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.When the F1 offspring mate with each other, the offspring are called the "F2" (second filial) generation.^ Mendel then crossed the F1 plants with each other to produce the F2 generation.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ Assuming again that the population is large, mating is random, evolutionary forces are absent, and Mendel's law of segregation holds, then in the offspring generation the frequency of the A i A i genotype will be p i 2 , and the frequency of the (unordered) A i A j genotype ( i ≠ j ) will be 2 p i p j .
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

One of the common diagrams used to predict the result of cross-breeding is the Punnett square.
.When studying human genetic diseases, geneticists often use pedigree charts to represent the inheritance of traits.^ The Amish, and their neighbors the Mennonites, have been studied by geneticists for some time because they are a genetically isolated community.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ DNA is sometimes referred to as the molecule of heredity as it is inherited and used to propagate traits.

^ Furthermore, the ability to study candidate genes in pedigrees where the candidate and disease are cosegregating will greatly enhance the chances of finding etiologic mutations.
  • Genetics 14 January 2010 4:14 UTC www.acnp.org [Source type: Academic]

[29] .These charts map the inheritance of a trait in a family tree.^ To identify these inherited factors, linkage analysis of multiplex families is being performed on a sample of 105 families with two or more affected sibs.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ These traits, from the Broader Phenotype Autism Symptom Scale (BPASS), were measured in nuclear families, each ascertained through two probands affected by autism spectrum disorder.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ The Human Genome Project has created maps of the rat and mouse genomes in addition to the human map, and these maps can be used to find genes controlling behavioral traits in these organisms.
  • Genetics 14 January 2010 4:14 UTC www.acnp.org [Source type: Academic]

Interactions of multiple genes

.Human height is a complex genetic trait.^ The special problems of applying molecular strategies to complex traits can be appreciated with an understanding of the genetic epidemiology of mental disorders and the theoretical underpinnings of the molecular genetic strategies.
  • Genetics 14 January 2010 4:14 UTC www.acnp.org [Source type: Academic]

^ Furthermore, finding genes responsible for Mendelian disease has become so straightforward that it is only a matter of time until all of these diseases have been mapped, and genetically complex traits are emerging as a new frontier of human genetics.
  • Genetics 14 January 2010 4:14 UTC www.acnp.org [Source type: Academic]

^ As a result, the field has achieved a more critical understanding of the difficulties of applying linkage to diseases of ambiguous etiology, genetics, and phenotype (i.e., "complex" genetic traits).
  • Genetics 14 January 2010 4:14 UTC www.acnp.org [Source type: Academic]

.Francis Galton's data from 1889 shows the relationship between offspring height as a function of mean parent height.^ Even if you know for sure that a puppy's parents carry a certain recessive trait, it's not a sure thing that the trait was passed to your puppy, unless the puppy shows the trait, or has offspring who show the trait.
  • Dachshund Puppies by Li'l Dachs - Li'l Dachs Genetics 14 January 2010 4:14 UTC www.lildachs.com [Source type: FILTERED WITH BAYES]

^ Collectively, these results show that the structure and function, but not the expression, of the GSH-requiring PGDS is conserved between chicken and rat.

^ (So for example, if a short and a tall organism mate, the height of the offspring will be intermediate between the two.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

While correlated, remaining variation in offspring heights indicates environment is also an important factor in this trait.
.Organisms have thousands of genes, and in sexually reproducing organisms assortment of these genes are generally independent of each other.^ Since these repeats and other junk DNA are between genes or in introns they have no apparent effect on an organisms function.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ An exception to independent assortment develops when genes appear near one another on the same chromosome.

^ At the same time if the two genes were on different chromosomes, inheriting one would be completely independent of and not affect the chance of inheriting the other because of the random chromosome shuffle.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

.This means that the inheritance of an allele for yellow or green pea color is unrelated to the inheritance of alleles for white or purple flowers.^ Even the rump colors are yellow with a slight green tinge to the upper portion.
  • Genetics 14 January 2010 4:14 UTC www.lovebirds.ca [Source type: FILTERED WITH BAYES]

^ Some alleles are recessive , which means that allele's trait will only be visible if the puppy inherits TWO of that recessive allele.
  • Dachshund Puppies by Li'l Dachs - Li'l Dachs Genetics 14 January 2010 4:14 UTC www.lildachs.com [Source type: FILTERED WITH BAYES]

^ In sweet peas, purple flower color (P) is dominant over white (p), but there is also a control gene such that if the plant has a C, the purple has permission to express itself.
  • Genetics Practice Problems 14 January 2010 4:14 UTC www.biology.clc.uc.edu [Source type: FILTERED WITH BAYES]

.This phenomenon, known as "Mendel's second law" or the "Law of independent assortment", means that the alleles of different genes get shuffled between parents to form offspring with many different combinations.^ The different forms of the genes are known as alleles.

^ What is the difference between gene families and multicopy genes?

^ The a y allele had to have come from the dam, meaning that she has at least one a y red allele in her "A" (Agouti) gene series.
  • Dachshund Puppies by Li'l Dachs - Li'l Dachs Genetics 14 January 2010 4:14 UTC www.lildachs.com [Source type: FILTERED WITH BAYES]

(Some genes do not assort independently, demonstrating .genetic linkage, a topic discussed later in this article.^ To help you understand how genetics work and to be able to determine the possible offsprings from different pairings I will divide this article into 6 main areas of discussion.
  • Genetics 14 January 2010 4:14 UTC www.lovebirds.ca [Source type: FILTERED WITH BAYES]

^ The relationship between the gene of classical (pre-molecular) genetics, and the gene of modern molecular genetics is a subtle and much discussed topic (cf.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

)
.Often different genes can interact in a way that influences the same trait.^ When this principle is used to explain an actual hereditary pattern, it is applied to genes that actually differed in the population exhibiting the pattern (often an experimental population).
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ These different types of diagrams complement each other by representing different "views" of the same information, presented in different ways for different purposes, but reusing most of the same graphical symbols.

^ The same DNA strand in 2 different individuals may result in different traits because of the effect of other DNA strands or the environment.

.In the Blue-eyed Mary (Omphalodes verna), for example, there exists a gene with alleles that determine the color of flowers: blue or magenta.^ Codominant "blue" and "purple" alleles would result in color blending and hence, violet flower petals.

^ Thus, there may exist a gene of moderate effect in this region.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ For example, in the case of blossom color, if the "red" allele is dominant to the "white" allele, in a heterozygous flower (with one red and one white allele), the petals will be red.

.Another gene, however, controls whether the flowers have color at all: color or white.^ The gene controlling color is Y linked.

^ The gene controlling color is autosomal.

^ The gene controlling color is X linked.

.When a plant has two copies of this white allele, its flowers are white – regardless of whether the first gene has blue or magenta alleles.^ Codominant "blue" and "purple" alleles would result in color blending and hence, violet flower petals.

^ For example, in the case of blossom color, if the "red" allele is dominant to the "white" allele, in a heterozygous flower (with one red and one white allele), the petals will be red.

^ History The existence of genes was first suggested by Gregor Mendel, who studied inheritance in pea plants and hypothesized a factor that conveys traits from parent to offspring.

.This interaction between genes is called epistasis, with the second gene epistatic to the first.^ This gene codes for an antigen that is called Rh factor because it was first discovered in Rh esus monkeys.
  • Genetics Practice Problems 14 January 2010 4:14 UTC www.biology.clc.uc.edu [Source type: FILTERED WITH BAYES]

^ A related difference is that Wright emphasized epistasis, or non-additive interactions between the genes within a single genome, to a much greater extent than Fisher or Haldane.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ Furthermore, statistical analysis also showed lack of any interaction between the observed allelic variants in the two HOX genes and autism.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

[30]
Many traits are not discrete features (eg. purple or white flowers) but are instead continuous features (eg. human height and skin color). .These complex traits are the product of many genes.^ The pathway to red eye pigment production begins at many distinct molecular genes and proceeds through several alternative branched pathways.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ These results support the hypothesis that GABA receptor subunit genes are involved in autism, most likely via complex gene-gene interactions.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ These theoretical explanations did not depend on ideas about what genes are, how genes are replicated, what genes do, or how differences in genes bring about differences in phenotypic traits.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

[31] .The influence of these genes is mediated, to varying degrees, by the environment an organism has experienced.^ Since these repeats and other junk DNA are between genes or in introns they have no apparent effect on an organisms function.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ The gene, called MET, regulates production of a protein that influences cell proliferation in various parts of the body.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ These findings indicate that genes account for 50 to 60 percent of the variance in the transmission of alcoholism ( 39 ).
  • Genetics 14 January 2010 4:14 UTC www.acnp.org [Source type: Academic]

.The degree to which an organism's genes contribute to a complex trait is called heritability.^ Coding regions in the genes of more complex organisms have introns .
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ Robert says that his framework focuses on organisms rather than genes and that it “takes seriously” the dynamical complexities of development emphasized by Keller.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ These aspects of inheritancethe interplay between genes and environment, the influence of many genesappear to be the norm with regard to many and perhaps most ("complex" or "multifactoral") traits.

[32] .Measurement of the heritability of a trait is relative – in a more variable environment, the environment has a bigger influence on the total variation of the trait.^ These aspects of inheritancethe interplay between genes and environment, the influence of many genesappear to be the norm with regard to many and perhaps most ("complex" or "multifactoral") traits.

^ The phenotype of an individual organism is either its total physical appearance and constitution, or a specific manifestation of a trait, such as size or eye color, that varies between individuals.

^ A pronounced variance contrast between haplotypes may also indicate the involvement of additional factors that influence the trait.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

.For example, human height is a complex trait with a heritability of 89% in the United States.^ They hold small, discreet conferences on the “missing heritability” problem: if all these human traits are heritable, why are GWAS studies failing so often?

In Nigeria, however, where people experience a more variable access to good nutrition and health care, height has a heritability of only 62%.[33]

Molecular basis for inheritance

DNA and chromosomes

The molecular structure of DNA. Bases pair through the arrangement of hydrogen bonding between the strands.
.The molecular basis for genes is deoxyribonucleic acid (DNA).^ We suggest that the tight binding of RC to lambda DNA is due to interaction of RC with other DNA-bound proteins, and is related to the molecular basis of the lambda cro- plasmid replication control.

^ Expression of molecular genes For various reasons, the relationship between DNA strand and a phenotype trait is not direct.

^ Deoxyribonucleic acid (DNA) is a nucleic acid which carries genetic instructions for the biological development of all cellular forms of life and many viruses.

.DNA is composed of a chain of nucleotides, of which there are four types: adenine (A), cytosine (C), guanine (G), and thymine (T).^ Chargaff had observed that the proportions of the four nucleotides vary between one DNA sample and the next, but that for particular pairs of nucleotides -- adenine and thymine, guanine and cytosine -- the two nucleotides are always present in equal proportions.

^ Each vine-like molecule is a strand of DNA: a chemically linked chain of nucleotides, each of which consists of a sugar, a phosphate and one of four kinds of Aromatic hydrocarbon "bases".

^ Because chemical dissection of DNA samples always yielded the same four nucleotides, the chemical composition of DNA appeared simple, perhaps even uniform.

.Genetic information exists in the sequence of these nucleotides, and genes exist as stretches of sequence along the DNA chain.^ A gene is a segment of nucleotides in one of the chains of a DNA molecule.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

^ The basic molecular concept, according to this analysis, is the concept of a gene for a linear sequence in a product of DNA expression: .
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

[34] .Viruses are the only exception to this rule—sometimes viruses use the very similar molecule RNA instead of DNA as their genetic material.^ RNA forms the genetic material of some viruses.

^ In genetics, transcription is the process of copying DNA to RNA by an enzyme called RNA polymerase (RNAP).

^ Double-stranded RNA Double-stranded RNA (or dsRNA) is RNA with two complementary strands, similar to the DNA found in all "higher" cells.

[35]
.DNA normally exists as a double-stranded molecule, coiled into the shape of a double-helix.^ Please draw a double stranded DNA molecule that has the sequence 5' AAGCT 3' .

^ In a vertically oriented double helix, the 3' strand is said to be ascending while the 5' strand is said to be descending.

^ Because of this directionality, close inspection of a double helix reveals that nucleotides are heading one way along one strand (the "ascending strand"), and the other way along the other strand (the "descending strand").

.Each nucleotide in DNA preferentially pairs with its partner nucleotide on the opposite strand: A pairs with T, and C pairs with G. Thus, in its two-stranded form, each strand effectively contains all necessary information, redundant with its partner strand.^ The polymerase catalyzes the sequence-specific incorporation of fluorescent nucleotides into nascent complementary strands on all the templates.

^ Under this idea, one might say that DNA contains information about development because DNA's effects on development were selected for in the process of evolution.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ According to the fundamental theory, genes and DNA direct all life processes by providing the information that specifies the development and functioning of organisms.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.This structure of DNA is the physical basis for inheritance: DNA replication duplicates the genetic information by splitting the strands and using each strand as a template for synthesis of a new partner strand.^ Synthesis RNA is made by an enzyme, RNA polymerase, using DNA as a template.

^ We suggest that the tight binding of RC to lambda DNA is due to interaction of RC with other DNA-bound proteins, and is related to the molecular basis of the lambda cro- plasmid replication control.

^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

[36]
.Genes are arranged linearly along long chains of DNA sequence, called chromosomes.^ The genes on the X chromosome are called sex-linked or X- linked genes.

^ All genes are arranged in a precise sequence on the chromosomes with the location of a specific gene called its locus.

^ The basic molecular concept, according to this analysis, is the concept of a gene for a linear sequence in a product of DNA expression: .
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.In bacteria, each cell usually contains a single circular chromosome, while eukaryotic organisms (which includes plants and animals) have their DNA arranged in multiple linear chromosomes.^ Chromosomes in bacteria Bacterial chromosomes are often circular but sometimes linear.

^ Eukaryotes possess multiple linear chromosomes contained in the cell's nucleus.

^ In living organisms DNA is organized in chromosomes and is located in the nucleus of each cell.

.These DNA strands are often extremely long; the largest human chromosome, for example, is about 247 million base pairs in length.^ A gene is often thousands of bases in length.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ As BRCA1 -/- tumors have characteristic abnormalities in DNA repair, and in maintenance of X chromosome inactivation, we explored these parameters in sporadic basal-like breast cancers.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ The largest known human protein has 27,000 amino acids corresponding to 81,000 DNA nucleotides.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

[37] .The DNA of a chromosome is associated with structural proteins that organize, compact, and control access to the DNA, forming a material called chromatin; in eukaryotes, chromatin is usually composed of nucleosomes, repeating units of DNA wound around a core of histone proteins.^ Chromatin structure in eukaryotes.

^ In the chromosomes of eukaryotes, the uncondensed DNA exists in a quasi-ordered structure inside the nucleus, where it wraps around histones (structural proteins, Fig.

^ We suggest that the tight binding of RC to lambda DNA is due to interaction of RC with other DNA-bound proteins, and is related to the molecular basis of the lambda cro- plasmid replication control.

[38] .The full set of hereditary material in an organism (usually the combined DNA sequences of all chromosomes) is called the genome.^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

^ According to the fundamental theory, genes and DNA direct all life processes by providing the information that specifies the development and functioning of organisms.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ Asexually reproducing species have one set of chromosomes, which is the same in all body cells.

.While haploid organisms have only one copy of each chromosome, most animals and many plants are diploid, containing two of each chromosome and thus two copies of every gene.^ The gametes they produce are haploid , meaning that they contain only one of each chromosome pair.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The organisms are assumed to be diploids , meaning that they contain two copies of each chromosome, one received from each parent.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ Some organisms are diploid - that is, they have paired homologous chromosomes in their somatic cells, and thus contain two copies of each gene.

[26] .The two alleles for a gene are located on identical loci of sister chromatids, each allele inherited from a different parent.^ An organism which has two different alleles of the gene is said to be heterozygous.

^ The different forms of the genes are known as alleles.

^ Yet, though the alleles of a gene differ in sequence, nevertheless they are regarded as a single gene (occupying a single locus).

.
Walther Flemming's 1882 diagram of eukaryotic cell division.
^ In most eukaryotes mitosis is accompanied with cell division or cytokinesis, but there are many exceptions, for instance among the fungi.

^ Chromosomes were first observed by Karl Wilhelm von Ngeli in 1842 and their behavior later described in detail by Walther Flemming in 1882.

^ In biology, mitosis is the process of chromosome segregation and nuclear division that follows replication of the genetic material in eukaryotic cells.

Chromosomes are copied, condensed, and organized. Then, as the cell divides, chromosome copies separate into the daughter cells.
.An exception exists in the sex chromosomes, specialized chromosomes many animals have evolved that play a role in determining the sex of an organism.^ Genes exist on both autosomal and on sex-chromosomes.
  • Genetics 14 January 2010 4:14 UTC www.lovebirds.ca [Source type: FILTERED WITH BAYES]

^ Many people found it difficult to accept that natural selection could play the explanatory role required of it by Darwin's theory.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ To determine the (diploid) number of chromosomes of an organism, cells can be locked in metaphase in vitro (in a reaction vial) with colchicine.

[39] .In humans and other mammals, the Y chromosome has very few genes and triggers the development of male sexual characteristics, while the X chromosome is similar to the other chromosomes and contains many genes unrelated to sex determination.^ The genes on the X chromosome are called sex-linked or X- linked genes.

^ It is the two sex chromosomes that determine if a fetus will become male or female.

^ For example, genes with similar functions are often kept close together in the nucleus, even if they are far apart on the chromosome.

.Females have two copies of the X chromosome, but males have one Y and only one X chromosome – this difference in X chromosome copy numbers leads to the unusual inheritance patterns of sex-linked disorders.^ Females will have two X chromosomes with only one being active while the male will have one X and one Y sex chromosomes.

^ The genes on the X chromosome are called sex-linked or X- linked genes.

^ Of these pairs of chromosomes, one is the sex chromosome.

Reproduction

.When cells divide, their full genome is copied and each daughter cell inherits one copy.^ Many species carry more than one copy of their genome within each of their somatic cells.

^ Plasmids that exist only as a single copy in each bacterium are, upon cell division, in danger of being lost in one of the segregating bacteria.

^ This process assures that each daughter nucleus receives a complete copy of the organism's genome.

This process, called mitosis, is the simplest form of reproduction and is the basis for asexual reproduction. .Asexual reproduction can also occur in multicellular organisms, producing offspring that inherit their genome from a single parent.^ While a brindled parent can produce solid colored offspring, be very careful when evaluating their solid colored puppies.
  • Dachshund Puppies by Li'l Dachs - Li'l Dachs Genetics 14 January 2010 4:14 UTC www.lildachs.com [Source type: FILTERED WITH BAYES]

^ When organisms reproduce the offspring tend to resemble their parents.

^ But in many cases, genes on the same chromosome that are inherited together produce offspring with unexpected allele combinations.

.Offspring that are genetically identical to their parents are called clones.^ Biology In biology, heredity refers to the transference of biological characteristics from a parent organism to offspring, and is practically a homonym for genetics, as genes are now recognized as the carriers of biological information.

.Eukaryotic organisms often use sexual reproduction to generate offspring that contain a mixture of genetic material inherited from two different parents.^ Genes are material entities that parents pass to offspring during reproduction.

^ Nearly all living things use the same genetic code, called the standard genetic code, although a few organisms use minor variations of the standard code.

^ They are not, however, identical to either parent, and they are not simply a mixture of the two parents.

.The process of sexual reproduction alternates between forms that contain single copies of the genome (haploid) and double copies (diploid).^ When the process is complete, two copies of the original double helix have been formed and hence the genes in the original DNA molecule have been effectively replicated.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ Mutations involving dark factors are identified by adding the terms Dark (single dark factor), or, Olive (double dark factor) for Green form birds, and, Dark (single dark factor), and, Mauve (Double Dark factor) to the phenotype.
  • Genetics 14 January 2010 4:14 UTC www.lovebirds.ca [Source type: FILTERED WITH BAYES]

^ The resulting diploid new MIC is homozygous for the entire haploid genome of the functional meiotic product saved in each conjugant.

[26] .Haploid cells fuse and combine genetic material to create a diploid cell with paired chromosomes.^ It is diploid and contains 5 pairs of chromosomes.

^ Human Genetics Human centromeres are the critical chromosome component necessary for proper segregation during cell division.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ To determine the (diploid) number of chromosomes of an organism, cells can be locked in metaphase in vitro (in a reaction vial) with colchicine.

.Diploid organisms form haploids by dividing, without replicating their DNA, to create daughter cells that randomly inherit one of each pair of chromosomes.^ It is diploid and contains 5 pairs of chromosomes.

^ Of these pairs of chromosomes, one is the sex chromosome.

^ In living organisms DNA is organized in chromosomes and is located in the nucleus of each cell.

.Most animals and many plants are diploid for most of their lifespan, with the haploid form reduced to single cell gametes.^ Most multi-celled animals, and many plants, have a lifecycle of this sort.
  • Population Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ Gametes are produced by meiosis of a diploid germ line cell.

^ In most eukaryotes mitosis is accompanied with cell division or cytokinesis, but there are many exceptions, for instance among the fungi.

.Although they do not use the haploid/diploid method of sexual reproduction, bacteria have many methods of acquiring new genetic information.^ Applications of plasmids Plasmids serve as important tools in genetics and biochemistry labs, where they are commonly used to multiply (make many copies of) or express particular genes.

^ In what is now known as Griffith's experiment, injections into a mouse of a deadly strain of a bacteria that had been heat-killed transferred genetic information to a safe strain of the same bacteria, killing the mouse.

^ Nearly all living things use the same genetic code, called the standard genetic code, although a few organisms use minor variations of the standard code.

.Some bacteria can undergo conjugation, transferring a small circular piece of DNA to another bacterium.^ Some of these enzymes unknot circular DNA by cleaving two strands so that another double-stranded segment can pass through.

[40] .Bacteria can also take up raw DNA fragments found in the environment and integrate them into their genome, a phenomenon known as transformation.^ In what is now known as Griffith's experiment, injections into a mouse of a deadly strain of a bacteria that had been heat-killed transferred genetic information to a safe strain of the same bacteria, killing the mouse.

^ For example, PCR can be used to introduce restriction enzyme sites, or to mutate (change) particular bases of DNA. PCR can also be used to determine whether a particular DNA fragment is found in a cDNA library.

^ In the complex cells that make up plants, animals and in other multi-celled organisms, most of the DNA is found in the chromosomes, which are located in the cell nucleus.

[41] .These processes result in horizontal gene transfer, transmitting fragments of genetic information between organisms that would be otherwise unrelated.^ Watson and Crick in 1953 published their famous paper A Structure for Deoxyribose Nucleic Acid describing the basic mechanism (the double helix ) whereby genetic information is recorded, copied, and transmitted in all living organisms.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ When a cell divides to form a second cell, the genetic information content is duplicated in a process called mitosis .
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

^ It boggles the mind to contemplate how long it could take to achieve these kinds of associations through the process of gene copying and transposition.
  • Genetics Summary 14 January 2010 4:14 UTC www.azinet.com [Source type: Academic]

Recombination and linkage

Thomas Hunt Morgan's 1916 illustration of a double crossover between chromosomes
.The diploid nature of chromosomes allows for genes on different chromosomes to assort independently during sexual reproduction, recombining to form new combinations of genes.^ The different forms of the genes are known as alleles.

^ The pair then breaks apart to form two chromosomes with a new combination of genes that differs from the combination supplied by the parents.

^ An exception to independent assortment develops when genes appear near one another on the same chromosome.

.Genes on the same chromosome would theoretically never recombine, however, were it not for the process of chromosomal crossover.^ An exception to independent assortment develops when genes appear near one another on the same chromosome.

^ But in many cases, genes on the same chromosome that are inherited together produce offspring with unexpected allele combinations.

^ However, alleles which are on the same chromosome more likely to be inherited together and are said to be linked.

.During crossover, chromosomes exchange stretches of DNA, effectively shuffling the gene alleles between the chromosomes.^ When the process is complete, two copies of the original double helix have been formed and hence the genes in the original DNA molecule have been effectively replicated.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ In an analysis of data from 204 autism families, the researchers identified an association between the disease and a common C allele in the MET gene promoter region.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ But in many cases, genes on the same chromosome that are inherited together produce offspring with unexpected allele combinations.

[42] .This process of chromosomal crossover generally occurs during meiosis, a series of cell divisions that creates haploid cells.^ During mitosis (cell division), the chromosomes are condensed and called metaphasic chromosomes.

^ Human Genetics Human centromeres are the critical chromosome component necessary for proper segregation during cell division.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ The transmission of genes from parent to offspring is carried out in a special process of cellular division called meiosis , which produces gamete cells containing one chromosome from each paired set.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.The probability of chromosomal crossover occurring between two given points on the chromosome is related to the distance between the points.^ There is much more chance of this happening if the alleles are far apart on the chromosome, as it is more likely that a cross-over will occur between them.

^ Additional potential susceptibility loci with two-point LOD scores > 2 were observed on chromosomes 1q21-22 and 7q.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ Genetic interactions, in genetics, are interactions that occur between two or more mutations that results in a new phenotype.

For an arbitrarily long distance, the probability of crossover is high enough that the inheritance of the genes is effectively uncorrelated. .For genes that are closer together, however, the lower probability of crossover means that the genes demonstrate genetic linkage – alleles for the two genes tend to be inherited together.^ Genetic linkage occurs when particular alleles are inherited together.

^ Nonetheless, mounting evidence for genetic linkage of autism to the chromosome 17q11.2 region that harbors the SERT locus (SLC6A4) supports a genetic effect at or near this gene.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ But in many cases, genes on the same chromosome that are inherited together produce offspring with unexpected allele combinations.

.The amounts of linkage between a series of genes can be combined to form a linear linkage map that roughly describes the arrangement of the genes along the chromosome.^ A study of the linkages between many genes enables the creation of a linkage map.

^ Gene maps show chromosomes containing linear arranged genes .

^ Further on, we will list these gene series and their alleles for you, and describe each one in as much detail as possible.
  • Dachshund Puppies by Li'l Dachs - Li'l Dachs Genetics 14 January 2010 4:14 UTC www.lildachs.com [Source type: FILTERED WITH BAYES]

[43]

Gene expression

Genetic code

The genetic code: DNA, through a messenger RNA intermediate, codes for protein with a triplet code.
.Genes generally express their functional effect through the production of proteins, which are complex molecules responsible for most functions in the cell.^ Through the proteins they encode, genes govern the cells in which they reside.

^ Each functional portion of this molecule is referred to as a gene.

^ Each human carries six to eight abnormal recessive genes but these genes do not cause cells to function abnormally except when two similar recessive genes are present.

.Proteins are chains of amino acids, and the DNA sequence of a gene (through RNA intermediate) is used to produce a specific protein sequence.^ The sequence of codons in a gene specifies the amino-acid sequence of the protein it encodes.

^ RNA into a protein also starts with a specific start and stop sequence.

^ So, this RNA sequence represents a protein sequence, three amino acids long.

.This process begins with the production of an RNA molecule with a sequence matching the gene's DNA sequence, a process called transcription.^ The resulting RNA molecule is the primary transcript.

^ In genetics, transcription is the process of copying DNA to RNA by an enzyme called RNA polymerase (RNAP).

^ However, for some gene sequences, RNA molecules are actually the functional end products.

.This messenger RNA molecule is then used to produce a corresponding amino acid sequence through a process called translation.^ These codons can then be translated with messenger RNA and then transfer RNA, with a codon corresponding to a particular amino acid.

^ So, this RNA sequence represents a protein sequence, three amino acids long.

^ In genetics, transcription is the process of copying DNA to RNA by an enzyme called RNA polymerase (RNAP).

.Each group of three nucleotides in the sequence, called a codon, corresponds to one of the twenty possible amino acids in protein – this correspondence is called the genetic code.^ The sequence of codons in a gene specifies the amino-acid sequence of the protein it encodes.

^ So, this RNA sequence represents a protein sequence, three amino acids long.

^ A sequence of three consecutive nucleotides, called a codon, is the protein-coding vocabulary.

[44] .The flow of information is unidirectional: information is transferred from nucleotide sequences into the amino acid sequence of proteins, but it never transfers from protein back into the sequence of DNA—a phenomenon Francis Crick called the central dogma of molecular biology.^ So, this RNA sequence represents a protein sequence, three amino acids long.

^ The sequence of codons in a gene specifies the amino-acid sequence of the protein it encodes.

^ In 1953, James D. Watson and Francis Crick demonstrated the molecular structure of DNA. Together, these discoveries established the central dogma of molecular biology, which states that proteins are transcribed from RNA which is translated from DNA. This dogma has since been shown to have exceptions, such as reverse transcription in retroviruses.

[45]
The dynamic structure of hemoglobin is responsible for its ability to transport oxygen within mammalian blood.
A single amino acid change causes hemoglobin to form fibers.
.The specific sequence of amino acids results in a unique three-dimensional structure for that protein, and the three-dimensional structures of protein are related to their function.^ The sequence of codons in a gene specifies the amino-acid sequence of the protein it encodes.

^ So, this RNA sequence represents a protein sequence, three amino acids long.

^ The polypeptide is ultimately folded into a 3-dimensional protein structure, which will go on to perform some specific function in the cell such as an enzyme subunit or cell membrane component.

[46][47] .Some are simple structural molecules, like the fibers formed by the protein collagen.^ The polypeptide is ultimately folded into a 3-dimensional protein structure, which will go on to perform some specific function in the cell such as an enzyme subunit or cell membrane component.

^ The instrumental roles of their protein products range from mechanical support of the cell structure to the transportation and manufacture of other molecules and to the regulation of other proteins' activities.

^ Rather, they are pairs of molecules, which entwine like vines to form a double helix (see the illustration at the right).

.Proteins can bind to other proteins and simple molecules, sometimes acting as enzymes by facilitating chemical reactions within the bound molecules (without changing the structure of the protein itself).^ We suggest that the tight binding of RC to lambda DNA is due to interaction of RC with other DNA-bound proteins, and is related to the molecular basis of the lambda cro- plasmid replication control.

^ DNA strand may also be silenced through DNA methylation or by chemical changes to the protein components of chromosomes (see histone).

^ The instrumental roles of their protein products range from mechanical support of the cell structure to the transportation and manufacture of other molecules and to the regulation of other proteins' activities.

.Protein structure is dynamic; the protein hemoglobin bends into slightly different forms as it facilitates the capture, transport, and release of oxygen molecules within mammalian blood.^ The instrumental roles of their protein products range from mechanical support of the cell structure to the transportation and manufacture of other molecules and to the regulation of other proteins' activities.

^ Each gene is transcribed into a short template molecule of the related polymer RNA, which is better suited for protein synthesis.

^ Within organisms, genetic information generally is carried in chromosomes, where it is represented in the chemical structure of particular DNA molecules.

.A single nucleotide difference within DNA can cause a single change in the amino acid sequence of a protein.^ The sequence of codons in a gene specifies the amino-acid sequence of the protein it encodes.

^ So, this RNA sequence represents a protein sequence, three amino acids long.

^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

.Because protein structures are the result of their amino acid sequences, some changes can dramatically change the properties of a protein by destabilizing the structure or changing the surface of the protein in a way that changes its interaction with other proteins and molecules.^ The sequence of codons in a gene specifies the amino-acid sequence of the protein it encodes.

^ So, this RNA sequence represents a protein sequence, three amino acids long.

^ We suggest that the tight binding of RC to lambda DNA is due to interaction of RC with other DNA-bound proteins, and is related to the molecular basis of the lambda cro- plasmid replication control.

.For example, sickle-cell anemia is a human genetic disease that results from a single base difference within the coding region for the β-globin section of hemoglobin, causing a single amino acid change that changes hemoglobin's physical properties.^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

^ Each human carries six to eight abnormal recessive genes but these genes do not cause cells to function abnormally except when two similar recessive genes are present.

^ Human Genetics Human centromeres are the critical chromosome component necessary for proper segregation during cell division.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

[48] .Sickle-cell versions of hemoglobin stick to themselves, stacking to form fibers that distort the shape of red blood cells carrying the protein.^ Messenger RNA is RNA that carries information from DNA to the ribosome sites of protein synthesis in the cell.

^ Genetics is the study of what make up an animals or plants.DNA carries all the information needed for protein synthesis and replication of cells.

.These sickle-shaped cells no longer flow smoothly through blood vessels, having a tendency to clog or degrade, causing the medical problems associated with this disease.^ Each human carries six to eight abnormal recessive genes but these genes do not cause cells to function abnormally except when two similar recessive genes are present.

^ The vast majority of mutations associated with human disease are loss-of-function mutations, but precisely what aspect of MeCP2 function is responsible for these phenotypes remains unknown.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ We investigated the consequences of these disease-associated mutations on neuroligin function.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

.Some genes are transcribed into RNA but are not translated into protein products – these are called non-coding RNA molecules.^ Most of these genes regulate protein folding, biogenesis, and degradation, suggesting the novel hypothesis that accumulation of damaged/misfolded proteins may be a mechanisms for osmosensation in animals.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ "Glimpsing the mammalian transcriptome's "other half:" Evolution, expression, and function of long non-protein-coding RNA" Dr. Leonard Lipovich Dept.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ These effects are linked to physical interactions of the dopamine-regulating gene products.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

.In some cases, these products fold into structures which are involved in critical cell functions (eg.^ The instrumental roles of their protein products range from mechanical support of the cell structure to the transportation and manufacture of other molecules and to the regulation of other proteins' activities.

^ The incorporation of 5-FU into mRNA at these high levels is sufficient to disrupt mRNA processing and protein synthesis so that even nondividing cells die of protein starvation .

^ The presence of regulatory polypeptides in these organisms cannot be ruled out, however, and genes which encode putative ALS/AHAS regulatory subunits have been identified in some cases .

.ribosomal RNA and transfer RNA).^ These amino acids are brought to the ribosome by what are known as transfer RNA which is a much smaller type of RNA. Each molecule of the transfer RNA will bring one amino acid to be used in the growing chain of protein.

^ Hence, according to her account, there are not process molecular genes for tRNA (transfer RNA), rRNA (ribosomal RNA) or snRNA (small nuclear RNA).
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ Some genes encode other elements such as ribosomal RNAs and transfer RNAs, both of which are involved in protein synthesis.

.RNA can also have regulatory effect through hybridization interactions with other RNA molecules (eg.^ Such RNA molecules include transfer RNA, ribosomal RNA, and RNA molecules that play regulatory and catalytic roles.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

microRNA).

Nature versus nurture

Siamese cats have a temperature-sensitive mutation in pigment production.
Although genes contain all the information an organism uses to function, the environment plays an important role in determining the ultimate phenotype—a phenomenon often referred to as "nature vs. nurture." The phenotype of an organism depends on the interaction of genetics with the environment. .One example of this is the case of temperature-sensitive mutations.^ Lets look at one example where a particular pair of genes is responsible for the development of the lutino (ino mutation of the normal green form).
  • Genetics 14 January 2010 4:14 UTC www.lovebirds.ca [Source type: FILTERED WITH BAYES]

^ For example, four-fold degenerate codons can tolerate any mutation at the third position; two-fold degenerate codons can tolerate one out of the three possible mutations at the third position.

^ For example, in the case of blossom color, if the "red" allele is dominant to the "white" allele, in a heterozygous flower (with one red and one white allele), the petals will be red.

.Often, a single amino acid change within the sequence of a protein does not change its behavior and interactions with other molecules, but it does destabilize the structure.^ The sequence of codons in a gene specifies the amino-acid sequence of the protein it encodes.

^ So, this RNA sequence represents a protein sequence, three amino acids long.

^ We suggest that the tight binding of RC to lambda DNA is due to interaction of RC with other DNA-bound proteins, and is related to the molecular basis of the lambda cro- plasmid replication control.

.In a high temperature environment, where molecules are moving more quickly and hitting each other, this results in the protein losing its structure and failing to function.^ The instrumental roles of their protein products range from mechanical support of the cell structure to the transportation and manufacture of other molecules and to the regulation of other proteins' activities.

^ The same DNA strand in 2 different individuals may result in different traits because of the effect of other DNA strands or the environment.

^ Collectively, these results show that the structure and function, but not the expression, of the GSH-requiring PGDS is conserved between chicken and rat.

.In a low temperature environment, however, the protein's structure is stable and functions normally.^ Newly synthesized polypeptides are linear sequences of amino acids that constitute proteins and proteins play a wide variety of functional roles in the cell and organism (and environment).
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The polypeptide is ultimately folded into a 3-dimensional protein structure, which will go on to perform some specific function in the cell such as an enzyme subunit or cell membrane component.

^ Amino acids, peptide bonds, polarity, primary structure, secondary structure, tertiary structure, quaternary structure, allosteric proteins, protein function, native and denatured configurations.

This type of mutation is visible in the coat coloration of Siamese cats, where a mutation in an enzyme responsible for pigment production causes it to destabilize and lose function at high temperatures.[49] The protein remains functional in areas of skin that are colder—legs, ears, tail, and face—and so the cat has dark fur at its extremities.
.Environment also plays a dramatic role in effects of the human genetic disease phenylketonuria.^ Patients harboring the latter mutations have progressive peripheral neuropathy, emphasizing the role of motor protein trafficking defects in human neurodegenerative disease.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ Newly synthesized polypeptides are linear sequences of amino acids that constitute proteins and proteins play a wide variety of functional roles in the cell and organism (and environment).
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ Phenopedia and Genopedia: disease-centered and gene-centered views of the evolving knowledge of human genetic associations -- Yu et al.
  • Genetics: human, medical, and clinical - �������� �������� 14 January 2010 4:14 UTC genetics.rusmedserv.com [Source type: Academic]

[50] .The mutation that causes phenylketonuria disrupts the ability of the body to break down the amino acid phenylalanine, causing a toxic build-up of an intermediate molecule that, in turn, causes severe symptoms of progressive mental retardation and seizures.^ Learning ability and social behavior deteriorated after seizure onset, with patients developing hyperactivity, inattention, aggression, autism, and mental retardation.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ Bacterially expressed wild-type StAR and four amino acid replacement/deletion mutants that cause lipoid CAH were purified to apparent homogeneity .

^ According to this simple account, a gene is a sequence of nucleotides in DNA that is transcribed into a sequence of nucleotides making up a messenger RNA molecule that is in turn translated into sequence of amino acids that forms a polypeptide.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.If someone with the phenylketonuria mutation follows a strict diet that avoids this amino acid, however, they remain normal and healthy.^ It spans about 150 amino acid residues, and begins as follows: .

^ Mutational analysis of KRAD-14 peptide revealed three adjacent amino acids, alteration of which greatly reduced the inhibitory potential of this peptide .

^ Following the principles of Mendelian inheritance, these crosses should have produced a mix of normal and rogue plants, but they produced only rogue plants.

.A popular method to determine how much role nature and nurture play is to study identical and fraternal twins or siblings of multiple birth.^ Our current studies examine the role played by NOS1AP, also termed CAPON, a gene linked to schizophrenia in regulating dendrite morphology.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ These studies indicate that the small subunit of the oxygenase is essential for activity but does not play a major role in determining the specificity of these enzymes.

^ Additionally, studies of genetic adaptation in Africa have important implications for identifying genes that play an important role in human evolution and disease.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

.October 2009" style="white-space:nowrap;">[citation needed] Because identical siblings come from the same zygote they are genetically the same.^ For example, in fruit flies the genes affecting eye color and wing length are inherited together because they appear on the same chromosome.

^ Identical twins share the same genotype, since their genomes are identical; but they never have the same phenotype, although their phenotypes may be very similar.

Fraternal siblings however are as different genetically from one another as normal siblings. .By comparing how often the twin of a set has the same disorder between fraternal and identical twins, scientists can see if there is more of a nature or nurture effect.^ Identical twins share the same genotype, since their genomes are identical; but they never have the same phenotype, although their phenotypes may be very similar.

^ There is much more chance of this happening if the alleles are far apart on the chromosome, as it is more likely that a cross-over will occur between them.

^ Here, we present data to demonstrate that the nature of genetic risk for cancer can vary between populations, even those typically thought to be of the same ethnicity.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

.One famous example of a multiple birth study includes the Genain quadruplets, who were identical quadruplets all diagnosed with schizophrenia.^ This seminar will illustrate successful experimental strategies using examples from our studies of schizophrenia, autism, and specific language impairment.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

[51]

Gene regulation

.The genome of a given organism contains thousands of genes, but not all these genes need to be active at any given moment.^ According to the fundamental theory, genes and DNA direct all life processes by providing the information that specifies the development and functioning of organisms.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ An individual who is heterozygous for all of these genes makes gametes.

^ Jablonka says that the sense of information in all these situations involve a source, a receiver system (organism or organism-designed system), and a special type of reaction of the receiver to the source.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.A gene is expressed when it is being transcribed into mRNA (and translated into protein), and there exist many cellular methods of controlling the expression of genes such that proteins are produced only when needed by the cell.^ Many of the genes encode widely expressed proteins orchestrating basic cellular processes (e.g.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ The information of development and function, which is passed down from one generation to the next, is allegedly encoded in the nucleotide sequences comprising genes and DNA. This so-called “genetic information” is first “transcribed” into RNA, then “translated” into proteins, and finally “expressed” in the development and functioning of organisms.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ Applications of plasmids Plasmids serve as important tools in genetics and biochemistry labs, where they are commonly used to multiply (make many copies of) or express particular genes.

.Transcription factors are regulatory proteins that bind to the start of genes, either promoting or inhibiting the transcription of the gene.^ The segments of a gene include (1) the transcribed unit … and any regulatory segments included in the transcription unit, and (2) the regulatory sequences that flank the trancription unit and are required for specific expression.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ I will discuss how we use various bioinformatic and comparative genomic approaches to target our molecular genetic analyses to specific genes and transcriptional regulatory elements.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ Gene regulation involves transcription factors that bind to DNA, which subsequently controls the expression profile.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

[52] .Within the genome of Escherichia coli bacteria, for example, there exists a series of genes necessary for the synthesis of the amino acid tryptophan.^ Within this region, residues 3147-3160 (KRAD-14) contain an exceptionally high proportion of positive amino acids .

^ We report here that they direct transcription from some but not all sigma32-type promoters when the respective rpoH genes are expressed in Escherichia coli .

^ A difference in the nucleotide sequence of a gene will result in the difference in the nucleotide sequence of RNA molecules, which in turn can result in a difference in the amino acid sequence of a polypeptide.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.However, when tryptophan is already available to the cell, these genes for tryptophan synthesis are no longer needed.^ The incorporation of 5-FU into mRNA at these high levels is sufficient to disrupt mRNA processing and protein synthesis so that even nondividing cells die of protein starvation .

^ However, no abnormalities were detected in any of the parents that were available for investigation.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ The presence of regulatory polypeptides in these organisms cannot be ruled out, however, and genes which encode putative ALS/AHAS regulatory subunits have been identified in some cases .

.The presence of tryptophan directly affects the activity of the genes—tryptophan molecules bind to the tryptophan repressor (a transcription factor), changing the repressor's structure such that the repressor binds to the genes.^ The instrumental roles of their protein products range from mechanical support of the cell structure to the transportation and manufacture of other molecules and to the regulation of other proteins' activities.

^ Gene regulation involves transcription factors that bind to DNA, which subsequently controls the expression profile.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ Cells regulate the activity of genes in part by increasing or decreasing their rate of transcription.

.The tryptophan repressor blocks the transcription and expression of the genes, thereby creating negative feedback regulation of the tryptophan synthesis process.^ Regulation of gene expression .

^ The segments of a gene include (1) the transcribed unit … and any regulatory segments included in the transcription unit, and (2) the regulatory sequences that flank the trancription unit and are required for specific expression.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ This chain of events involving RNA transcription, and polypeptide translation is referred to as gene expression.

[53]
Transcription factors bind to DNA, influencing the transcription of associated genes.
.Differences in gene expression are especially clear within multicellular organisms, where cells all contain the same genome but have very different structures and behaviors due to the expression of different sets of genes.^ Because each discipline models the biology of life differently, the material entity that supports the gene in one discipline is not the same as in the other.

^ Nearly all living things use the same genetic code, called the standard genetic code, although a few organisms use minor variations of the standard code.

^ An organism which has two different alleles of the gene is said to be heterozygous.

.All the cells in a multicellular organism derive from a single cell, differentiating into variant cell types in response to external and intercellular signals and gradually establishing different patterns of gene expression to create different behaviors.^ While a single gene cannot create normal behaviors, mutations in a single gene can disrupt them.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ We compared gene expression patterns from in the regenerative model of neurite extension from dorsal root ganglion neurons and found overlapping clusters of genes associated with regenerative activity.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ In multicellular organisms they control the development of the individual from the fertilized egg and the day-to-day functions of the cells that make up tissues and organs.

.As no single gene is responsible for the development of structures within multicellular organisms, these patterns arise from the complex interactions between many cells.^ In multicellular organisms they control the development of the individual from the fertilized egg and the day-to-day functions of the cells that make up tissues and organs.

^ These observations support a model in which accumulation of (p)ppGpp, in response to starvation, initiates the program of fruiting body development, including the production of A-factor.

^ Many species carry more than one copy of their genome within each of their somatic cells.

.Within eukaryotes there exist structural features of chromatin that influence the transcription of genes, often in the form of modifications to DNA and chromatin that are stably inherited by daughter cells.^ Chromatin structure in eukaryotes.

^ The gene, called MET, regulates production of a protein that influences cell proliferation in various parts of the body.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ When the process is complete, two copies of the original double helix have been formed and hence the genes in the original DNA molecule have been effectively replicated.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

[54] .These features are called "epigenetic" because they exist "on top" of the DNA sequence and retain inheritance from one cell generation to the next.^ (This is the entire sequence of one DNA strand.

^ These variations are called mutations, but, Only if they can be inherited.
  • Genetics 14 January 2010 4:14 UTC www.lovebirds.ca [Source type: FILTERED WITH BAYES]

^ The study of inherited features not strictly associated with changes in the DNA sequence is called epigenetics.

.Because of epigenetic features, different cell types grown within the same medium can retain very different properties.^ The same DNA strand in 2 different individuals may result in different traits because of the effect of other DNA strands or the environment.

^ Because each discipline models the biology of life differently, the material entity that supports the gene in one discipline is not the same as in the other.

^ Because there is some crossing over of DNA when the chromosomes segregate, alleles on the same chromosome can be separated and go to different cells.

.Although epigenetic features are generally dynamic over the course of development, some, like the phenomenon of paramutation, have multigenerational inheritance and exist as rare exceptions to the general rule of DNA as the basis for inheritance.^ Although not all features show these patterns of Mendelian inheritance, his work acted as a proof that application of statistics to inheritance could be highly useful.

^ Manipulation of DNA can in turn alter the inheritance and features of various organisms.

^ The study of inherited features not strictly associated with changes in the DNA sequence is called epigenetics.

[55]

Genetic change

Mutations

Gene duplication allows diversification by providing redundancy: one gene can mutate and lose its original function without harming the organism.
.During the process of DNA replication, errors occasionally occur in the polymerization of the second strand.^ When the process is complete, two copies of the original double helix have been formed and hence the genes in the original DNA molecule have been effectively replicated.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The A form appears likely to occur only in dehydrated samples of DNA, such those used in crystallography experiments, and possibly in hybrid pairings of DNA and RNA strands.

^ The two resulting double strands are generally almost perfectly identical, but occasionally errors in replication can result in a less than perfect copy (see mutation), and each of them consists of one original and one newly synthesized strand.

.These errors, called mutations, can have an impact on the phenotype of an organism, especially if they occur within the protein coding sequence of a gene.^ Errors that occur in the synthesis are known as mutations.

^ Physical changes in genes are called mutations .

^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

.Error rates are usually very low—1 error in every 10–100 million bases—due to the "proofreading" ability of DNA polymerases.^ The polymerase chain reaction is an extremely versatile technique for copying DNA. In brief, PCR allows a single DNA sequence to be copied (millions of times), or altered in predetermined ways.

[56][57] .(Without proofreading error rates are a thousand-fold higher; because many viruses rely on DNA and RNA polymerases that lack proofreading ability, they experience higher mutation rates.^ In genetics, transcription is the process of copying DNA to RNA by an enzyme called RNA polymerase (RNAP).

^ The energy-generating organelles known as chloroplasts and mitochondria also carry DNA, as do many viruses.

^ The A form appears likely to occur only in dehydrated samples of DNA, such those used in crystallography experiments, and possibly in hybrid pairings of DNA and RNA strands.

) .Processes that increase the rate of changes in DNA are called mutagenic: mutagenic chemicals promote errors in DNA replication, often by interfering with the structure of base-pairing, while UV radiation induces mutations by causing damage to the DNA structure.^ Physical changes in genes are called mutations .

^ In genetics, transcription is the process of copying DNA to RNA by an enzyme called RNA polymerase (RNAP).

^ DNA strand may also be silenced through DNA methylation or by chemical changes to the protein components of chromosomes (see histone).

[58] .Chemical damage to DNA occurs naturally as well, and cells use DNA repair mechanisms to repair mismatches and breaks in DNA—nevertheless, the repair sometimes fails to return the DNA to its original sequence.^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

^ DNA is sometimes referred to as the molecule of heredity as it is inherited and used to propagate traits.

^ The A form appears likely to occur only in dehydrated samples of DNA, such those used in crystallography experiments, and possibly in hybrid pairings of DNA and RNA strands.

.In organisms that use chromosomal crossover to exchange DNA and recombine genes, errors in alignment during meiosis can also cause mutations.^ According to the fundamental theory, genes and DNA direct all life processes by providing the information that specifies the development and functioning of organisms.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The mutations (differences in genes) identified by the Morgan group (e.g., the purple mutation) have been routinely identified as differences in nucleotide sequences in DNA. .
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The origin, terminus and other DNA regions show three migration patterns during active partitioning of daughter chromosomes.

[59] .Errors in crossover are especially likely when similar sequences cause partner chromosomes to adopt a mistaken alignment; this makes some regions in genomes more prone to mutating in this way.^ These properties of the genetic code make it more fault-tolerant for mutations.

^ Human Genetics, Emory University., School of Medicine Human chromosome errors of segregation during gamete formation are the leading cause of pregnancy loss and birth defects.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ This is not the case with many other actual difference makers, such as polymerases, which are more like on/off switches (with respect to differences in linear sequences).
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.These errors create large structural changes in DNA sequence—duplications, inversions or deletions of entire regions, or the accidental exchanging of whole parts between different chromosomes (called translocation).^ The ends of the chromosomes are special structures called telomeres.

^ Every plasmid contains at least one DNA sequence that serves as an origin of replication or ori (a starting point for DNA replication), which enables the plasmid DNA to be duplicated independently from the chromosomal DNA. .

^ DNA strand may also be silenced through DNA methylation or by chemical changes to the protein components of chromosomes (see histone).

Natural selection and evolution

.Mutations alter an organisms genotype and occasionally this causes different phenotypes to appear.^ Even two organisms with identical genotypes normally differ in their phenotypes.

^ A phenotype is said to be canalized if mutations (changes in the genome) do not noticeably affect the physical properties of the organism.

^ If there is little plasticity, the phenotype of an organism can be reliably predicted from knowledge of the genotype, regardless of environmental peculiarities during development.

.Most mutations have little effect on an organism's phenotype, health, or reproductive fitness.^ A phenotype is said to be canalized if mutations (changes in the genome) do not noticeably affect the physical properties of the organism.

^ If there is little plasticity, the phenotype of an organism can be reliably predicted from knowledge of the genotype, regardless of environmental peculiarities during development.

Mutations that do have an effect are usually deleterious, but occasionally some can be beneficial. .Studies in the fly Drosophila melanogaster suggest that if a mutation changes a protein produced by a gene, about 70 percent of these mutations will be harmful with the remainder being either neutral or weakly beneficial.^ Physical changes in genes are called mutations .

^ Comparative sequence analyses of these clones suggested that certain point mutations seemed to be related to the loss of proteolytic activity .

^ These names were originally the names of the specific genes in which mutation of each of these stop codons was first detected.

[60]
An evolutionary tree of eukaryotic organisms, constructed by comparison of several orthologous gene sequences
Population genetics studies the distribution of genetic differences within populations and how these distributions change over time.[61] .Changes in the frequency of an allele in a population is mainly influenced by natural selection, where a given allele provides a selective or reproductive advantage to the organism,[62] as well as other factors such as genetic drift, artificial selection and migration.^ The foundational discipline is population genetics which studies the distribution of and change in allele frequencies of genes under the influence of the four evolutionary forces: natural selection, genetic drift, mutation and migration.

^ While molecular genetics studies the structure and function of genes at a molecular level, ecological genetics focuses on wild populations of organisms, and attempts to collect data on the ecological aspects of individuals as well as molecular markers from those individuals.

^ The Hershey-Chase experiment proves the genetic information of phages (and all other organisms) to be DNA .

[63]
.Over many generations, the genomes of organisms can change significantly, resulting in the phenomenon of evolution.^ A phenotype is said to be canalized if mutations (changes in the genome) do not noticeably affect the physical properties of the organism.

^ Finally, the sequenced parts are rearranged in silico, resulting in the genome sequence of the sequenced organism.

^ In many species of organism, only a small fraction of the total sequence of the genome appears to encode protein.

Selection for beneficial mutations can cause a species to evolve into forms better able to survive in their environment, a process called adaptation.[64] .New species are formed through the process of speciation, often caused by geographical separations that prevent populations from exchanging genes with each other.^ Discovery through evolutionary conservation Motifs have been discovered by studying similar genes in different species.

^ The pair then breaks apart to form two chromosomes with a new combination of genes that differs from the combination supplied by the parents.

^ In common speech, "gene" is often used to refer to the hereditary cause of a trait, disease or conditionas in "the gene for obesity."

[65] .The application of genetic principles to the study of population biology and evolution is referred to as the modern synthesis.^ The word "gene" is shared by many disciplines, including classical genetics, molecular genetics, evolutionary biology and population genetics.

^ Population, quantitative and ecological genetics are all very closely related subfields and also build upon classical genetics (supplemented with modern molecular genetics).

^ Knowledge of the genetic population boundaries within Africa has important implications for the design and implementation of disease association studies in Africans and African Americans, and for reconstructing modern human origins.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

.By comparing the homology between different species genomes it is possible to calculate the evolutionary distance between them and when they may have diverged (called a molecular clock).^ Identical twins share the same genotype, since their genomes are identical; but they never have the same phenotype, although their phenotypes may be very similar.

^ However they may carry different form of a gene.

^ Discovery through evolutionary conservation Motifs have been discovered by studying similar genes in different species.

[66] .Genetic comparisons are generally considered a more accurate method of characterizing the relatedness between species than the comparison of phenotypic characteristics.^ Larvae with these traits have a higher chance of survival when exposed to the predators, but grow more slowly than other phenotypes.

^ Many species carry more than one copy of their genome within each of their somatic cells.

.December 2009" style="white-space:nowrap;">[citation needed] The evolutionary distances between species can be used to form evolutionary trees – these trees represent the common descent and divergence of species over time, although they do not show the transfer of genetic material between unrelated species (known as horizontal gene transfer and most common in bacteria).^ The different forms of the genes are known as alleles.

^ In what is now known as Griffith's experiment, injections into a mouse of a deadly strain of a bacteria that had been heat-killed transferred genetic information to a safe strain of the same bacteria, killing the mouse.

^ These aspects of inheritancethe interplay between genes and environment, the influence of many genesappear to be the norm with regard to many and perhaps most ("complex" or "multifactoral") traits.

Research and technology

Model organisms and genetics

The common fruit fly (Drosophila melanogaster) is a popular model organism in genetics research.
.Although geneticists originally studied inheritance in a wide range of organisms, researchers began to specialize in studying the genetics of a particular subset of organisms.^ The Amish, and their neighbors the Mennonites, have been studied by geneticists for some time because they are a genetically isolated community.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ In modern research, genetics provides important tools in the investigation of the function of a particular gene, e.g.

^ Nearly all living things use the same genetic code, called the standard genetic code, although a few organisms use minor variations of the standard code.

.The fact that significant research already existed for a given organism would encourage new researchers to choose it for further study, and so eventually a few model organisms became the basis for most genetics research.^ Nearly all living things use the same genetic code, called the standard genetic code, although a few organisms use minor variations of the standard code.

^ While forward genetic screens are productive, a more straightforward approach would be to determine the phenotype that results from mutating a given gene.

^ It would emerge upon the discovery of DNA's structure, but few researchers imagined that DNA's structure had much to say about genetics.

[67] .Common research topics in model organism genetics include the study of gene regulation and the involvement of genes in development and cancer.^ In modern research, genetics provides important tools in the investigation of the function of a particular gene, e.g.

^ According to the fundamental theory, genes and DNA direct all life processes by providing the information that specifies the development and functioning of organisms.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ In an analysis of data from 204 autism families, the researchers identified an association between the disease and a common C allele in the MET gene promoter region.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

.Organisms were chosen, in part, for convenience—short generation times and easy genetic manipulation made some organisms popular genetics research tools.^ Within organisms, genetic information generally is carried in chromosomes, where it is represented in the chemical structure of particular DNA molecules.

^ In modern research, genetics provides important tools in the investigation of the function of a particular gene, e.g.

.Widely used model organisms include the gut bacterium Escherichia coli, the plant Arabidopsis thaliana, baker's yeast (Saccharomyces cerevisiae), the nematode Caenorhabditis elegans, the common fruit fly (Drosophila melanogaster), and the common house mouse (Mus musculus).^ Mutat Res, 1998 Mar 13, 399(1), 55 - 64 Transgenic nematodes as biomonitors of microwave-induced stress; Daniells C et al.; Transgenic nematodes (Caenorhabditis elegans strain PC72), carrying a stress-inducible reporter gene (Escherichia coli beta-galactosidase) under the control of a C .

^ They usually occur in bacteria, sometimes in eukaryotic organisms (e.g., the 2-micrometre-ring in Saccharomyces cerevisiae).

Medical genetics research

.Medical genetics seeks to understand how genetic variation relates to human health and disease.^ Researchers have known for years that damaged DNA can lead to human diseases such as cancer, but how damage occurs--and what causes it--has remained less clear.

^ Latent genetically influenced traits, which may be related only indirectly to the classic disease symptoms defined in ICD-10 or DSM-IV are known as endophenotypes.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ Both types of variation are likely to have a major impact on humans, including their health and susceptibility to disease.

[68] .When searching for an unknown gene that may be involved in a disease, researchers commonly use genetic linkage and genetic pedigree charts to find the location on the genome associated with the disease.^ Latest Research : Genetics 'Molecular assassin' targets disease gene .

^ Applications of plasmids Plasmids serve as important tools in genetics and biochemistry labs, where they are commonly used to multiply (make many copies of) or express particular genes.

^ In modern research, genetics provides important tools in the investigation of the function of a particular gene, e.g.

.At the population level, researchers take advantage of Mendelian randomization to look for locations in the genome that are associated with diseases, a technique especially useful for multigenic traits not clearly defined by a single gene.^ Within a sequence or database of sequences, researchers search and find motifs using computer-based techniques of sequence analysis, such as BLAST. Such techniques belong to the discipline of bioinformatics.

^ The observation that some genes do not segregate independently at meiosis, broke the laws of Mendelian inheritance, and provided science with a way to map characteristics to a location on the chromosomes.

^ For this reason, two or more patterns are often associated with a single motif: the defining pattern, and various typical patterns.

[69] .Once a candidate gene is found, further research is often done on the same gene (called an orthologous gene) in model organisms.^ Because each discipline models the biology of life differently, the material entity that supports the gene in one discipline is not the same as in the other.

^ Nearly all living things use the same genetic code, called the standard genetic code, although a few organisms use minor variations of the standard code.

^ An organism in which both copies of the gene are identical - that is, have the same allele - is said to be homozygous for that gene.

.In addition to studying genetic diseases, the increased availability of genotyping techniques has led to the field of pharmacogenetics—studying how genotype can affect drug responses.^ Molecular genetics is the field of biology which studies the structure and function of genes at a molecular level.

[70]
Although it is not usually an inherited disease, cancer is a genetic disease.[71] The process of cancer development in the body is a combination of events. .Mutations occasionally occur within cells in the body as they divide.^ A body's genetic materials can be found within the nucleus of each of its cells.

.While these mutations will not be inherited by any offspring, they can affect the behavior of cells, sometimes causing them to grow and divide more frequently.^ Each human carries six to eight abnormal recessive genes but these genes do not cause cells to function abnormally except when two similar recessive genes are present.

^ In an actual cell, where a population of unprocessed RNA molecules differ with respect to linear sequence, the question arises: what causes these differences?
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ To identify these inherited factors, linkage analysis of multiplex families is being performed on a sample of 105 families with two or more affected sibs.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

.There are biological mechanisms that attempt to stop this process; signals are given to inappropriately dividing cells that should trigger cell death, but sometimes additional mutations occur that cause cells to ignore these messages.^ Each human carries six to eight abnormal recessive genes but these genes do not cause cells to function abnormally except when two similar recessive genes are present.

^ Cell Biology, University of Alabama at Birmingham, AL I will discuss how our studies of sperm and egg communication are providing insight into the biological functions of VAPB genes, which when mutated in humans causes ALS. .
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

^ In addition to the role in the sensory signaling process, the thalamus is also involved in other brain functions.
  • Department of Genetics » Rutgers University 14 January 2010 4:14 UTC genetics.rutgers.edu [Source type: Academic]

.An internal process of natural selection occurs within the body and eventually mutations accumulate within cells to promote their own growth, creating a cancerous tumor that grows and invades various tissues of the body.^ The gene, called MET, regulates production of a protein that influences cell proliferation in various parts of the body.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ Once amplified, even low-level damage signals become strong enough to activate the cell's natural repair processes while the injury is most tractable to repair.

^ A body's genetic materials can be found within the nucleus of each of its cells.

Research techniques

.DNA can be manipulated in the laboratory.^ When they do, they are typically referring to a set of laboratory techniques aimed at identifying and/or manipulating DNA segments involved in the synthesis of important biological molecules.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

.Restriction enzymes are a commonly used enzyme that cuts DNA at specific sequences, producing predictable fragments of DNA.[72] DNA fragments can be visualized through use of gel electrophoresis, which separates fragments according to their length.^ In agarose gel electrophoresis, DNA and RNA can be separated based on size by running the DNA through an agarose gel.

^ Proteins can also be separated based on their electric charge, using what is known as an isoelectric gel...

^ The basic principle is that DNA, RNA, and proteins can all be separated using an electric field.

The use of ligation enzymes allows DNA fragments to be reconnected, and by ligating fragments of DNA together from different sources, researchers can create recombinant DNA. Often associated with genetically modified organisms, recombinant DNA is commonly used in the context of plasmids – short circular DNA fragments with a few genes on them. .By inserting plasmids into bacteria and growing those bacteria on plates of agar (to isolate clones of bacteria cells), researchers can clonally amplify the inserted fragment of DNA (a process known as molecular cloning).^ This plasmid can be inserted into either bacterial or animal cells.

^ We suggest that the tight binding of RC to lambda DNA is due to interaction of RC with other DNA-bound proteins, and is related to the molecular basis of the lambda cro- plasmid replication control.

^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

(Cloning can also refer to the creation of clonal organisms, through various techniques.)
E coli colonies on a plate of agar, an example of cellular cloning and often used in molecular cloning.
.DNA can also be amplified using a procedure called the polymerase chain reaction (PCR).^ Polymerase chain reaction (PCR) Main article: Polymerase chain reaction .

^ In genetics, transcription is the process of copying DNA to RNA by an enzyme called RNA polymerase (RNAP).

^ The polymerase chain reaction is an extremely versatile technique for copying DNA. In brief, PCR allows a single DNA sequence to be copied (millions of times), or altered in predetermined ways.

[73] .By using specific short sequences of DNA, PCR can isolate and exponentially amplify a targeted region of DNA. Because it can amplify from extremely small amounts of DNA, PCR is also often used to detect the presence of specific DNA sequences.^ This definition emphasizes that regulatory sequences as well as coding regions are required for “specific expression.” Only a small proportion of coding sequences are transcribed in a given cell at a particular time, and whether a particular sequence is transcribed depends in part on regulatory regions external to the coding region.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

^ The polymerase chain reaction is an extremely versatile technique for copying DNA. In brief, PCR allows a single DNA sequence to be copied (millions of times), or altered in predetermined ways.

^ But this account shows that genes and DNA play a distinctive causal role in that genes are the causally specific actual difference makers of difference in the linear sequences of unprocessed RNA molecules.
  • Molecular Genetics (Stanford Encyclopedia of Philosophy) 14 January 2010 4:14 UTC plato.stanford.edu [Source type: Academic]

DNA sequencing and genomics

.One of the most fundamental technologies developed to study genetics, DNA sequencing allows researchers to determine the sequence of nucleotides in DNA fragments.^ In genetics terminology, sequencing is most often restricted to determining the nucleotides of a DNA or RNA strand.

^ (This is the entire sequence of one DNA strand.

^ The genetic code is a set of rules, which maps DNA sequences to proteins in the living cell, and is employed in the process of protein synthesis.

.Developed in 1977 by Frederick Sanger and coworkers, chain-termination sequencing is now routinely used to sequence DNA fragments.^ The polymerase chain reaction is an extremely versatile technique for copying DNA. In brief, PCR allows a single DNA sequence to be copied (millions of times), or altered in predetermined ways.

^ Currently, most such sequencing is performed using the chain termination method; however, this can only be used to identify fairly short sequences (around 300-1000 base pairs on ABI machine), and must therefore be used as the basis for more complex techniques, such as chromosome walking and shotgun sequencing.

^ For example, PCR can be used to introduce restriction enzyme sites, or to mutate (change) particular bases of DNA. PCR can also be used to determine whether a particular DNA fragment is found in a cDNA library.

[74] .With this technology, researchers have been able to study the molecular sequences associated with many human diseases.^ In an analysis of data from 204 autism families, the researchers identified an association between the disease and a common C allele in the MET gene promoter region.
  • neurodiversity.com | autism & genetics 20 September 2009 9:13 UTC www.neurodiversity.com [Source type: Academic]

^ In a joint effort, researchers from the European Molecular Biology Laboratory (EMBL) and the University of Heidelberg, Germany, have now discovered that HH is a liver disease.

^ Researchers have known for years that damaged DNA can lead to human diseases such as cancer, but how damage occurs--and what causes it--has remained less clear.

.As sequencing has become less expensive, researchers have sequenced the genomes of many organisms, using computational tools to stitch together the sequences of many different fragments (a process called genome assembly).^ Applications of plasmids Plasmids serve as important tools in genetics and biochemistry labs, where they are commonly used to multiply (make many copies of) or express particular genes.

^ Nearly all living things use the same genetic code, called the standard genetic code, although a few organisms use minor variations of the standard code.

^ Within a sequence or database of sequences, researchers search and find motifs using computer-based techniques of sequence analysis, such as BLAST. Such techniques belong to the discipline of bioinformatics.

[75] .These technologies were used to sequence the human genome, leading to the completion of the Human Genome Project in 2003.[23] New high-throughput sequencing technologies are dramatically lowering the cost of DNA sequencing, with many researchers hoping to bring the cost of resequencing a human genome down to a thousand dollars.^ April) Successful completion of Human Genome Project with 99% of the genome sequenced to a 99.99% accuracy .

^ BACs are often used in sequencing other organisms, in genome projects, for example the Human Genome Project.

^ These amino acids are brought to the ribosome by what are known as transfer RNA which is a much smaller type of RNA. Each molecule of the transfer RNA will bring one amino acid to be used in the growing chain of protein.

[76]
.The large amount of sequence data available has created the field of genomics, research that uses computational tools to search for and analyze patterns in the full genomes of organisms.^ Within a sequence or database of sequences, researchers search and find motifs using computer-based techniques of sequence analysis, such as BLAST. Such techniques belong to the discipline of bioinformatics.

^ Another major use of plasmids is to make large amounts of proteins.

^ BACs are often used in sequencing other organisms, in genome projects, for example the Human Genome Project.

.Genomics can also be considered a subfield of bioinformatics, which uses computational approaches to analyze large sets of biological data.^ Within a sequence or database of sequences, researchers search and find motifs using computer-based techniques of sequence analysis, such as BLAST. Such techniques belong to the discipline of bioinformatics.


See also

Notes

  1. ^ Genetikos, Henry George Liddell, Robert Scott, "A Greek-English Lexicon", at Perseus
  2. ^ Genesis, Henry George Liddell, Robert Scott, "A Greek-English Lexicon", at Perseus
  3. ^ Online Etymology Dictionary
  4. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Genetics and the Organism: Introduction". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.60. 
  5. ^ Hartl D, Jones E (2005)
  6. ^ Weiling, F (1991). "Historical study: Johann Gregor Mendel 1822–1884.". American journal of medical genetics 40 (1): 1–25; discussion 26. doi:10.1002/ajmg.1320400103. PMID 1887835. 
  7. ^ Lamarck, J-B (2008). In Encyclopædia Britannica. Retrieved from Encyclopædia Britannica Online on 16 March 2008.
  8. ^ Peter J. Bowler, The Mendelian Revolution: The Emergency of Hereditarian Concepts in Modern Science and Society (Baltimore: Johns Hopkins University Press, 1989): chapters 2 & 3.
  9. ^ a b Blumberg, Roger B.. "Mendel's Paper in English". http://www.mendelweb.org/Mendel.html. 
  10. ^ genetics, n., Oxford English Dictionary, 3rd ed.
  11. ^ Bateson W. "Letter from William Bateson to Alan Sedgwick in 1905". The John Innes Centre. http://www.jic.ac.uk/corporate/about/bateson.htm. Retrieved 15 March 2008. . Note that the letter was to an Adam Sedgwick, a zoologist at Trinity College, Cambridge, not "Alan", and not to be confused with the renown British geologist, Adam Sedgwick, who lived some time earlier.
  12. ^ genetic, adj., Oxford English Dictionary, 3rd ed.
  13. ^ Bateson, W (1907). "The Progress of Genetic Research". in Wilks, W. Report of the Third 1906 International Conference on Genetics: Hybridization (the cross-breeding of genera or species), the cross-breeding of varieties, and general plant breeding. London: Royal Horticultural Society. 
    Initially titled the "International Conference on Hybridisation and Plant Breeding", Wilks changed the title for publication as a result of Bateson's speech.[citation needed]
  14. ^ Moore, JOHN A. (1983). "Thomas Hunt Morgan—The Geneticist". Integrative and Comparative Biology 23: 855. doi:10.1093/icb/23.4.855. 
  15. ^ Sturtevant AH (1913). "The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association". Journal of Experimental Biology 14: 43–59. http://www.esp.org/foundations/genetics/classical/holdings/s/ahs-13.pdf. 
  16. ^ Avery, O. T. (1944). "STUDIES ON THE CHEMICAL NATURE OF THE SUBSTANCE INDUCING TRANSFORMATION OF PNEUMOCOCCAL TYPES: INDUCTION OF TRANSFORMATION BY A DESOXYRIBONUCLEIC ACID FRACTION ISOLATED FROM PNEUMOCOCCUS TYPE III". Journal of Experimental Medicine 79: 137. doi:10.1084/jem.79.2.137.  Reprint: Avery, OT; Macleod; Mccarty (1979). "Studies on the chemical nature of the substance inducing transformation of pneumococcal types. Inductions of transformation by a desoxyribonucleic acid fraction isolated from pneumococcus type III.". The Journal of experimental medicine 149 (2): 297–326. doi:10.1084/jem.149.2.297. PMID 33226. 
  17. ^ Hershey, AD; Chase (1952). "Independent functions of viral protein and nucleic acid in growth of bacteriophage.". The Journal of general physiology 36 (1): 39–56. doi:10.1085/jgp.36.1.39. PMID 12981234. 
  18. ^ Judson, Horace (1979). The Eighth Day of Creation: Makers of the Revolution in Biology. Cold Spring Harbor Laboratory Press. pp. 51–169. ISBN 0-87969-477-7. 
  19. ^ Watson, J. D.; Crick (1953). "Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid". Nature 171: 737. doi:10.1038/171737a0. http://www.nature.com/nature/dna50/watsoncrick.pdf. 
  20. ^ Watson, J. D.; Crick (1953). "Genetical Implications of the Structure of Deoxyribonucleic Acid". Nature 171: 964. doi:10.1038/171964b0. http://www.nature.com/nature/dna50/watsoncrick2.pdf. 
  21. ^ Sanger, F; Nicklen; Coulson (1977). "DNA sequencing with chain-terminating inhibitors.". Proceedings of the National Academy of Sciences of the United States of America 74 (12): 5463–7. doi:10.1073/pnas.74.12.5463. PMID 271968. 
  22. ^ Saiki, RK; Scharf; Faloona; Mullis; Horn; Erlich; Arnheim (1985). "Enzymatic amplification of beta-globin genomic sequences and restriction site analysis for diagnosis of sickle cell anemia.". Science (New York, N.Y.) 230 (4732): 1350–4. doi:10.1126/science.2999980. PMID 2999980. 
  23. ^ a b "Human Genome Project Information". Human Genome Project. http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml. Retrieved 15 March 2008. 
  24. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Patterns of Inheritance: Introduction". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.199. 
  25. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Mendel's experiments". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.200. 
  26. ^ a b c Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Mendelian genetics in eukaryotic life cycles". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.484. 
  27. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Interactions between the alleles of one gene". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.630. 
  28. ^ Cheney, Richard W.. "Genetic Notation". http://faculty.users.cnu.edu/rcheney/Genetic%20Notation.htm. Retrieved 18 March 2008. 
  29. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Human Genetics". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.229. 
  30. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Gene interaction and modified dihybrid ratios". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.644. 
  31. ^ Mayeux, R (2005). "Mapping the new frontier: complex genetic disorders.". The Journal of clinical investigation 115 (6): 1404–7. doi:10.1172/JCI25421. PMID 15931374. 
  32. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Quantifying heritability". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.4009. 
  33. ^ Luke, A; Guo; Adeyemo; Wilks; Forrester; Lowe W; Comuzzie; Martin et al. (2001). "Heritability of obesity-related traits among Nigerians, Jamaicans and US black people.". International journal of obesity and related metabolic disorders : journal of the International Association for the Study of Obesity 25 (7): 1034–41. doi:10.1038/sj.ijo.0801650. PMID 11443503. 
  34. ^ Pearson, H (2006). "Genetics: what is a gene?". Nature 441 (7092): 398–401. doi:10.1038/441398a. PMID 16724031. 
  35. ^ Prescott, L (1993). Microbiology. Wm. C. Brown Publishers. ISBN 0697013723. 
  36. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Mechanism of DNA Replication". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.1523. 
  37. ^ Gregory, SG; Barlow; Mclay; Kaul; Swarbreck; Dunham; Scott; Howe et al. (2006). "The DNA sequence and biological annotation of human chromosome 1.". Nature 441 (7091): 315–21. doi:10.1038/nature04727. PMID 16710414. 
  38. ^ Alberts et al. (2002), II.4. DNA and chromosomes: Chromosomal DNA and Its Packaging in the Chromatin Fiber
  39. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Sex chromosomes and sex-linked inheritance". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.222. 
  40. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Bacterial conjugation". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.1304. 
  41. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Bacterial transformation". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.1343. 
  42. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Nature of crossing-over". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.929. 
  43. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Linkage maps". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.899. 
  44. ^ Berg JM, Tymoczko JL, Stryer L, Clarke ND (2002). "I. 5. DNA, RNA, and the Flow of Genetic Information: Amino Acids Are Encoded by Groups of Three Bases Starting from a Fixed Point". Biochemistry (5th ed.). New York: W. H. Freeman and Company. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=stryer.section.685. 
  45. ^ Crick, F (1970). "Central dogma of molecular biology.". Nature 227 (5258): 561–3. PMID 4913914. http://www.nature.com/nature/focus/crick/pdf/crick227.pdf. 
  46. ^ Alberts et al. (2002), I.3. Proteins: The Shape and Structure of Proteins
  47. ^ Alberts et al. (2002), I.3. Proteins: Protein Function
  48. ^ "How Does Sickle Cell Cause Disease?". Brigham and Women's Hospital: Information Center for Sickle Cell and Thalassemic Disorders. 11 April 2002. http://sickle.bwh.harvard.edu/scd_background.html. Retrieved 23 July 2007. 
  49. ^ Imes, DL; Geary; Grahn; Lyons (2006). "Albinism in the domestic cat (Felis catus) is associated with a tyrosinase (TYR) mutation.". Animal genetics 37 (2): 175–8. doi:10.1111/j.1365-2052.2005.01409.x. PMID 16573534. 
  50. ^ "MedlinePlus: Phenylketonuria". NIH: National Library of Medicine. http://www.nlm.nih.gov/medlineplus/phenylketonuria.html. Retrieved 15 March 2008. 
  51. ^ Rosenthal, David (1964). The Genain quadruplets; a case study and theoretical analysis of heredity and environment in schizophrenia.. New York: Basic Books. ISBN B0000CM68F. 
  52. ^ Brivanlou, AH; Darnell Je (2002). "Signal transduction and the control of gene expression.". Science (New York, N.Y.) 295 (5556): 813–8. doi:10.1126/science.1066355. PMID 11823631. 
  53. ^ Alberts et al. (2002), II.3. Control of Gene Expression – The Tryptophan Repressor Is a Simple Switch That Turns Genes On and Off in Bacteria
  54. ^ Jaenisch, R; Bird (2003). "Epigenetic regulation of gene expression: how the genome integrates intrinsic and environmental signals.". Nature genetics 33 Suppl: 245–54. doi:10.1038/ng1089. PMID 12610534. 
  55. ^ Chandler, VL (2007). "Paramutation: from maize to mice.". Cell 128 (4): 641–5. doi:10.1016/j.cell.2007.02.007. PMID 17320501. 
  56. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Spontaneous mutations". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.2706. 
  57. ^ Freisinger, E; Grollman; Miller; Kisker (2004). "Lesion (in)tolerance reveals insights into DNA replication fidelity.". The EMBO journal 23 (7): 1494–505. doi:10.1038/sj.emboj.7600158. PMID 15057282. 
  58. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Induced mutations". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.2727. 
  59. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Chromosome Mutation I: Changes in Chromosome Structure: Introduction". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.2844. 
  60. ^ Sawyer, SA; Parsch; Zhang; Hartl (2007). "Prevalence of positive selection among nearly neutral amino acid replacements in Drosophila.". Proceedings of the National Academy of Sciences of the United States of America 104 (16): 6504–10. doi:10.1073/pnas.0701572104. PMID 17409186. 
  61. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Variation and its modulation". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.3842. 
  62. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Selection". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.3886. 
  63. ^ Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). "Random events". An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=iga.section.3906. 
  64. ^ Darwin, Charles (1859). On the Origin of Species (1st ed.). London: John Murray. pp. 1. http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=text&pageseq=16. . Related earlier ideas were acknowledged in Darwin, Charles (1861). On the Origin of Species (3rd ed.). London: John Murray. xiii. http://darwin-online.org.uk/content/frameset?itemID=F381&viewtype=text&pageseq=20. 
  65. ^ Gavrilets, S (2003). "Perspective: models of speciation: what have we learned in 40 years?". Evolution; international journal of organic evolution 57 (10): 2197–215. doi:10.1554/02-727. PMID 14628909. 
  66. ^ Wolf, YI; Rogozin; Grishin; Koonin (2002). "Genome trees and the tree of life.". Trends in genetics : TIG 18 (9): 472–9. doi:10.1016/S0168-9525(02)02744-0. PMID 12175808. 
  67. ^ "The Use of Model Organisms in Instruction". University of Wisconsin: Wisconsin Outreach Research Modules. http://www.loci.wisc.edu/outreach/text/model.html. Retrieved 15 March 2008. 
  68. ^ "NCBI: Genes and Disease". NIH: National Center for Biotechnology Information. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=gnd&ref=sidebar. Retrieved 15 March 2008. 
  69. ^ Davey Smith, G; Ebrahim (2003). "'Mendelian randomization': can genetic epidemiology contribute to understanding environmental determinants of disease?". International journal of epidemiology 32 (1): 1–22. doi:10.1093/ije/dyg070. PMID 12689998. 
  70. ^ "Pharmacogenetics Fact Sheet". NIH: National Institute of General Medical Sciences. http://www.nigms.nih.gov/Initiatives/PGRN/Background/FactSheet.htm. Retrieved 15 March 2008. 
  71. ^ Strachan T, Read AP (1999). Human Molecular Genetics 2 (second ed.). John Wiley & Sons Inc.. Chapter 18: Cancer Genetics
  72. ^ Lodish et al. (2000), Chapter 7: 7.1. DNA Cloning with Plasmid Vectors
  73. ^ Lodish et al. (2000), Chapter 7: 7.7. Polymerase Chain Reaction: An Alternative to Cloning
  74. ^ Brown TA (2002). "Section 2, Chapter 6: 6.1. The Methodology for DNA Sequencing". Genomes 2 (2nd ed.). Oxford: Bios. ISBN 1 85996 228 9. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=genomes.section.6452. 
  75. ^ Brown (2002), Section 2, Chapter 6: 6.2. Assembly of a Contiguous DNA Sequence
  76. ^ Service, RF (2006). "Gene sequencing. The race for the $1000 genome.". Science (New York, N.Y.) 311 (5767): 1544–6. doi:10.1126/science.311.5767.1544. PMID 16543431. 

References

  • Alberts B, Johnson A, Lewis J, Raff M, Roberts K, and Walter P (2002). Molecular Biology of the Cell (4th ed.). New York: Garland Science. ISBN 0-8153-3218-1. 
  • Griffiths, Anthony J. F.; Miller, Jeffrey H.; Suzuki, David T. et al., eds (2000). An Introduction to Genetic Analysis (7th ed.). New York: W. H. Freeman. ISBN 0-7167-3520-2. 
  • Hartl D, Jones E (2005). Genetics: Analysis of Genes and Genomes (6th ed.). Jones & Bartlett. ISBN 0-7637-1511-5. 
  • Lodish H, Berk A, Zipursky LS, Matsudaira P, Baltimore D, and Darnell J (2000). Molecular Cell Biology (4th ed.). New York: Scientific American Books. ISBN 0-7167-3136-3. 
  • Witzany, Guenther, ed (2009). Natural Genetic Engineering and Natural Genome Editing. New York: Annals of the New York Academy of Sciences. [1]

External links



Study guide

Up to date as of January 14, 2010

From Wikiversity

.Craig Venter's work in creating synthetic life Crain Ventor's, who co-mapped the Human Genome, has created synthetic life by building DNA base by base and planting it into bacteria.^ A comprehensive genome-based atlas, created by researchers, would help shed light on healthy and abnormal kidney development and disease.

^ A bacterial artificial chromosome (BAC) is a DNA construct, based on a fertility plasmid, used for transforming and cloning in bacteria, usually E. coli.

^ Emory University scientists have identified and created a map of more than 400,000 insertions and deletions (INDELs) in the human genome that signal a little-explored type of genetic difference among individuals.

He created a company that is developing Algae that convert CO2 and sunlight into fuel. Exxon has invested $600 million into the company.

Wikibooks

Up to date as of January 23, 2010
(Redirected to General Genetics article)

From Wikibooks, the open-content textbooks collection

Contents

  1. Introduction
  2. Basics of Heredity
  3. Genetic Principles
    1. Dominant and Recessive Genes
    2. Mendelian Inheritance
    3. Non-Mendelian Genetics
  4. Molecular Genetics
    1. Genomes
    2. Chromosomes
    3. The DNA Molecule
      1. The Discovery of the DNA Molecule
      2. Structure of the DNA Molecule
    4. Gene Expression
      1. Gene Expression in Eukaryotes
      2. Gene Expression in Prokaryotes
      3. Transcription
      4. RNA processing
        1. Capping
        2. Splicing
        3. Polyadenylation
        4. Editing
        5. Nuclear Export
        6. RNA surveillance
      5. Translation
      6. Regulation of Gene Expression
      7. Gene Control of Proteins
    5. Recombinant DNA Cloning Technology
    6. Molecular Evolution
    7. Transposition
  5. Developmental Genetics
  6. Population Genetics
    1. Hardy-Weinberg Equilibrium
    2. Fisher-Wright Model
    3. Neutral Theory of Molecular Evolution
    4. Genetics, Ecology, and Modern Synthesis Theory
  7. Behavioral Genetics
  8. Quantitative Genetics
  9. Mutations and Evolution
  10. Diseases and Genes
    1. Linking Diseases with Associated Genes
    2. Genetic Predispositions for Diseases
    3. Case studies:
      1. Cystic Fibrosis
      2. Obesity and the Leptin Protein
      3. Cancer
  11. Pharmacogenetics
  12. Ethical Issues
    1. Reproductive Cloning
    2. Cloning for Research

External Links

  • Roche Genetics Education Program [1]
  • Medical-Genetics.com[2]

Related books


Simple English

Genetics is a discipline of biology.[1] It is the science of heredity and variation of traits (characteristics) in living organisms, and the study of genes.[2][3][4] In the laboratory, genetics proceeds by mating carefully selected organisms, and analysing their offspring. More informally, genetics is the study of how parents pass some of their characteristics to their children. It is an important part of biology, and gives the basic rules on which evolution acts.

The fact that living things inherit traits from their parents has been known since prehistoric times, and used to improve crop plants and animals through selective breeding. However, the modern science of genetics, which seeks to understand the process of inheritance, only began with the work of Gregor Mendel in the mid-nineteenth century.[5] Although he did not know the physical basis for heredity, Mendel observed that organisms inherit traits via discrete units of inheritance, which are now called genes.

Contents

DNA

Living things are made of millions of tiny self-contained components called cells. Inside of each cell are long molecules called DNA.[6] DNA stores information that tells the cells how to create that living thing. Parts of this information that tell how to make one small part or characteristic of the living thing – red hair, or blue eyes, or a tendency to be tall – are known as genes.

Every cell in the same living thing has the same DNA, but only some of it is used in each cell. For instance, some genes that tell how to make parts of the liver are switched off in the brain. What genes are used can also change over time. For instance, a lot of genes are used by a child early in pregnancy that are not used later.

A living thing has two copies of each gene, one from its mother, and one from its father.[7] There can be multiple types of each gene, which give different instructions: one version might cause a person to have blue eyes, another might cause them to have brown. These different versions are known as alleles of the gene.

Since a living thing has two copies of each gene, it can have two different alleles of it at the same time. Often, one allele will be dominant, meaning that the living thing looks and acts as if it had only that one allele. The unexpressed allele is called recessive. In other cases, you end up with something in between the two possibilities. In that case, the two alleles are called co-dominant.

Most of the characteristics that you can see in a living thing have multiple genes that influence them. And many genes have multiple effects on the body, because their function will not have the same effect in each tissue. The multiple effects of a single gene is called pleiotropism. The whole set of genes is called the genotype, and the total effect of genes on the body is called the phenotype. These are key terms in genetics.

History of Genetics

Pre-Mendelian ideas

We know that man started breeding domestic animals from early times, probably before the invention of agriculture. We do not know when heredity was first appreciated as a scientific problem. The Greeks, and most obviously Aristotle, studied living things, and proposed ideas about reproduction and heredity.[8]

Probably the most important idea before Mendel was that of Charles Darwin, whose idea of pangenesis had two parts. The first, that persistent hereditary units were passed on from one generation to another, was quite right. The second was his idea that they were replenished by 'gemmules' from the somatic (body) tissues. This was entirely wrong, and plays no part in science today.[9] Darwin was right about one thing: whatever happens in evolution must happen by means of heredity, and so an accurate science of genetics is fundamental to the theory of evolution. This 'mating' between genetics and evolution took many years to organise. It resulted in the Modern evolutionary synthesis.

Mendelian Genetics

The basic rules of genetics were first discovered by a monk named Gregor Mendel in around 1865. For thousands of years, people had already studied how traits are inherited from parents to their children. However, Mendel's work was different because he designed his experiments very carefully.

In his experiments, Mendel studied how traits were passed on in pea plants. He started his crosses with plants that bred true, and counted characters that were eirther/or in nature (either tall or short). He bred large numbers of plants, and expressed his results numerically. He used test crosses to reveal the presence and proportion of recessive characters.

Mendel explained the results of his experiment using two scientific laws:

  • 1. Factors, later called genes, normally occur in pairs in ordinary body cells, yet separate during the formation of sex cells. These factors determine the organism's traits, and are inherited from its parents. When gametes are produced by meiosis, the two factors separate. A gamete only receives one or the other. This Mendel called the Law of segregation.
  • 2. Alleles of different genes separate independently of one another when gametes are formed. This he called the Law of Independent Assortment. So Mendel thought that different traits are inherited independently of one another. We now know this is only true if the genes are not on the same chromosome, in which case they are not linked to each other.

Mendel's laws helped explain the results he observed in his pea plants. Later, geneticists discovered that his laws were also true for other living things, even humans. Mendel's findings from his work on the garden pea plants helped to establish the field of genetics. His contributions were not limited to the basic rules that he discovered. Mendel's care towards controlling experiment conditions along with his attention to his numerical results set a standard for future experiments. Over the years, scientists have changed and improved Mendel's ideas. However, the science of genetics would not be possible today without the early work of Gregor Mendel.

Between Mendel and modern genetics

In the years between Mendel's work and 1900 the foundations of cytology, the study of cells, was developed. The facts discovered about the nucleus and cell division were essential for Mendel's work to be properly understood.[10]

1832: Barthélémy Dumortier, the first to observe cell division in a multicellular organism.[10][11]
1841, 1852: Robert Remak (1815–1865), a Jewish PolishGerman physiologist, was the first person to state the foundation of cell biology: that cells only derive from other cells. This was later popularized by the German doctor Rudolf Virchow (1821–1902), who used the famous phrase omnis cellula e cellula, meaning, all cells from other cells.
1865: Gregor Mendel's paper, Experiments on plant hybridization was published.
1876: Meiosis was discovered and described for the first time in sea urchin eggs, by German biologist Oscar Hertwig (1849–1922).
1878–1888: Walther Flemming and Eduard Strasburger describe chromosome behaviour during mitosis.[12][13]
1883: Meiosis was described at the level of chromosomes, by Belgian zoologist Edouard van Beneden (1846–1910), in Ascaris (roundworm) eggs.
1883: German zoologist Wilhelm Roux (1850–1924) realised the significance of the linear structure of chromosomes. Their splitting into two equal longitudinal halves assured each daughter cell got the same chromosome complement. Therefore, chromosomes were the bearers of heredity.[14]
1889: Dutch botanist Hugo de Vries suggests that "inheritance of specific traits in organisms comes in particles", naming such particles (pan)genes.[15]
1890: The significance of meiosis for reproduction and inheritance was described only in 1890 by German biologist August Weismann (1834–1914), who noted that two cell divisions were necessary to transform one diploid cell into four haploid cells if the number of chromosomes had to be maintained.
1902–1904: Theodor Boveri (1862–1915), a German biologist, in a series of papers, drew attention to the correspondence between the behaviour of chromosomes and the results obtained by Mendel.[16] He said that chromosomes were "independent entities which retain their independence even in the resting nucleua... What comes out of the nucleus is what goes into it".
1903: Walter Sutton suggested that chromosomes, which segregate in a Mendelian fashion, are hereditary units.[17] Edmund B. Wilson (1856–1939), Sutton's teacher, and the author of one of the most famous text-books in biology,[18] called this the Sutton–Boveri hypothesis.

At this point, discoveries in cytology merged with the rediscovered ideas of Mendel to make a fusion called cytogenetics, (cyto = cell; genetics = heredity) which has continued to the present day.

Rediscovery of Mendel's work

During the 1890s several biologists began doing experiments on breeding. and soon Mendel's results were duplicated, even before his papers were read. Carl Correns and Hugo de Vries were the main rediscovers of Mendel's writings and laws. Both acknowledged Mendel's priority, although it is probable that de Vries did not understand his own results until after reading Mendel.[19] Though Erich von Tschermak was originally also credited with rediscovery, this is no longer accepted because he did not understand Mendel's laws.[20] Though de Vries later lost interest in Mendelism, other biologists built genetics into a science.[19]

Mendel's results were replicated, and genetic linkage soon worked out. William Bateson perhaps did the most in the early days to publicise Mendel's theory. The word genetics, and other terminology, originated with Bateson.

Mendel's experimental results have later been the object of some debate. Fisher analyzed the results of the F2 (second filial) ratio and found them to be implausibly close to the exact ratio of 3 to 1.[21] It is sometimes suggested that Mendel may have censored his results, and that his seven traits each occur on a separate chromosome pair, an extremely unlikely occurrence if they were chosen at random. In fact, the genes Mendel studied occurred in only four linkage groups, and only one gene pair (out of 21 possible) is close enough to show deviation from independent assortment; this is not a pair that Mendel studied.[22]

Tools of Genetics

Punnett Squares

Developed by Reginald Punnett, Punnett squares are used by biologists to determine the probability of offspring to having a particular genotype.

Maternal
B b
Paternal B BB Bb
b Bb bb

If B represents the allele for having black hair and b represents the allele for having white hair, the offspring of two Bb parents would have a 25% probability of having two white hair alleles (bb), 50% of having one of each (Bb), and 25% of having only black hair alleles (BB).

Pedigree chart

Geneticists (biologists who study genetics) use pedigree charts to record traits of people in a family. Using these charts, geneticists can study how a trait is inherited from person to person.

Geneticists can also use pedigree charts to predict how traits will be passed to future children in a family. For instance, genetic counselors are professionals who work with families who might be affected by genetic diseases. As part of their job, they create pedigree charts for the family, which can be used to study how the disease might be inherited.

Twin studies

Since human beings are not bred experimentally, human genetics must be studied by other means. One way is by twin studies. Identical twins are natural clones. They carry the same genes, they may be used to investigate how much heredity contributes to individual people. Studies with twins have been quite interesting. If we make a list of characteristic traits, we find that they vary in how much they owe to heredity. For example:

  • Eye colour: entirely inherited
  • Weight, height: partly inherited, partly environmental
  • Which language a person speaks: entirely environmental.

The way the studies are done is like this. Take a group of identical twins and a group of fraternal twins. Measure them for various traits. Do a statistical analysis (such as analysis of variance). This tells you to what extent the trait is inherited. Those traits which are partly inherited will be significantly more similar in identical twins. Studies like this may be carried further, by comparing identical twins brought up together with identical twins brought up in different circumstances. That gives a handle on how much circumstances can alter the outcomes of genetically identical people.

The person who first did twin studies was Francis Galton, Darwin's half-cousin, who was a founder of statistics. His method was to trace twins through their life-history, making many kinds of measurement. Unfortunately, though he knew about mono and dizygotic twins, he did not appreciate the real genetic difference.[23][24] Twin studies of the modern kind did not appear until the 1920s.

References

  1. The word comes from the Ancient Greek for origin
  2. King R.C. Stansfield W.D. & Mulligan P.K. 2006. A dictionary of genetics, 7th ed. Oxford.
  3. Griffiths A.J.H. et al 2000. An introduction to genetic analysis. 7th ed, Freeman, New York. ISBN 0-7167-3520-2 [1]
  4. Hartl D. & Jones E. 2005. Genetics: analysis of genes and genomes. 6th ed, Jones & Bartlett. ISBN 0-7637-1511-5.
  5. Weiling F. Weiling, F (1991). [Expression error: Unexpected < operator "Historical study: Johann Gregor Mendel 1822-1884"]. American Journal of Medical Genetics 40 (1): 1–25; discussion 26. doi:10.1002/ajmg.1320400103. PMID 1887835. 
  6. There are a few exceptions to this – red blood cells lose their DNA and most of their other structures before going into the blood, for instance.
  7. Again, mostly true: Some types of living things only have one parent. Also, some living things have only one copy of each gene (bacteria, for example) and some plants have an extra set. Some genes come from only one parent, like genes on the human Y chromosome which is passed only from father to son.
  8. Stubbe, Hans 1972. History of genetics: from prehistoric times to the rediscovery of Mendel's laws, transl. by T.R.W. Waters. MIT Press, Cambridge, MA. Chapter 2.
  9. Olby, Robert 1985. Origins of Mendelism. 2nd ed, Chicago: University of Chicago Press. p84–85 ISBN 0-226-62591-5.
  10. 10.0 10.1 Harris, Henry 1995. The cells of the body: a history of somatic cell genetics Cold Spring Harbor Laboratory, Plainview N.Y.
  11. Dumortier B. 1832. Researches sur la structure comparée et le développement des animaux et des végétaux. Nova Acta Phys.-Med. Acad. Caesar. Leopold.-Carolinae Nat. Curios., part 1. 16, 217–311.
  12. Flemming, Walther 1882. Beitrage zur Kenntnis der Zelle und ihrer Lebenserscheinungen. Vogel, Leipzig.
  13. Strasburger, Eduard 1880. Zellbildung und Zelltheilung. Dabis, Jena.
  14. Roux W. 1883. Uber die Bedeutung der Kerntheilungsfiguren. Engelmann, Leipzig.
  15. Vries, H. de (1889) Intracellular Pangenesis [2] ("pan-gene" definition on page 7 and 40 of this 1910 translation)
  16. Boveri T. 1904. Ergebnisse uber die Konstitution der chromatischen Substanz des Zellkerns. Fischer, Jena.
  17. Ernest W. Crow and James F. Crow (2002-01-01). "100 Years Ago: Walter Sutton and the chromosome theory of heredity". Genetics 160 (1): 1–4. PMID 11805039. http://www.genetics.org/cgi/content/full/160/1/1. 
  18. Wilson E.B. 1896; 1900; 1925. The cell. Macmillan, London. The third edition ran to 1232 pages.
  19. 19.0 19.1 Bowler, Peter J. (2003). Evolution: the history of an idea. Berkeley: University of California Press. ISBN 0-520-23693-9. 
  20. Mayr E. (1982). The growth of biological thought. Cambridge: The Belknap Press of Harvard University Press. pp. 730. ISBN 0-674-36446-5. 
  21. Fisher R.A. 1936. Has Mendel's work been rediscovered? Annals of Science 1:115-137.
  22. Carlson E.A. 2004. Mendel's legacy. Cold Spring Harbor Laboratory.
  23. Bulmer M. 2000. Francis Galton, pioneer of heredity and biometry. Johns Hopkins, Baltimore MD. p67
  24. Galton F. 1875. The history of twins, as a criterion of the relative powers of nature and nurture. J. Anthropological Inst. 5, 329–348.


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