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Genetic variation is the difference in
DNA Deoxyribonucleic acid (; DNA) is a molecule A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically Electricity is the set of physical ...

DNA
among individuals or the differences between populations. The multiple sources of genetic variation include
mutation In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechan ...
and
genetic recombination Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, ph ...
. Mutations are the ultimate sources of genetic variation, but other mechanisms, such as
sexual reproduction Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Greek, ...
and
genetic drift Genetic drift (allelic drift or the Sewall Wright effect) is the change in the frequency of an existing gene In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical stru ...

genetic drift
, contribute to it, as well.


Among individuals within a population

Genetic variation can be identified at many levels. Identifyinggenetic variation is possible from observations of
phenotypic In genetics Genetics is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular inter ...

phenotypic
variation in either quantitative traits (traits that vary continuously and are coded for by many genes (e.g., leg length in dogs)) or discrete traits (traits that fall into discrete categories and are coded for by one or a few genes (e.g., white, pink, or red petal color in certain flowers)). Genetic variation can also be identified by examining variation at the level of enzymes using the process of protein electrophoresis. Polymorphic genes have more than one allele at each locus. Half of the genes that code for enzymes in insects and plants may be polymorphic, whereas polymorphisms are less common among vertebrates. Ultimately, genetic variation is caused by variation in the order of bases in the
nucleotide Nucleotides are organic molecules , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's ability to Catenation, ...

nucleotide
s in genes. New technology now allows scientists to directly sequence DNA, which has identified even more genetic variation than was previously detected by protein electrophoresis. Examination of DNA has shown genetic variation in both coding regions and in the noncoding intron region of genes. Genetic variation will result in phenotypic variation if variation in the order of nucleotides in the
DNA sequence DNA sequencing is the process of determining the nucleic acid sequence A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides Nucleotides are organic ...

DNA sequence
results in a difference in the order of
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
s in proteins coded by that DNA sequence, and if the resultant differences in amino-acid sequence influence the shape, and thus the function of the enzyme.


Between populations

Geographic variation means genetic differences in populations from different locations. This is caused by
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of peta ...
or
genetic drift Genetic drift (allelic drift or the Sewall Wright effect) is the change in the frequency of an existing gene In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical stru ...

genetic drift
.


Measurement

Genetic variation within a population is commonly measured as the percentage of polymorphic gene loci or the percentage of gene loci in heterozygous individuals.


Sources

Random
mutation In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechan ...
s are the ultimate source of genetic variation. Mutations are likely to be rare, and most mutations are neutral or deleterious, but in some instances, the new alleles can be favored by natural selection.
Polyploidy Polyploidy is a condition in which the cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse ...
is an example of chromosomal mutation. Polyploidy is a condition wherein organisms have three or more sets of genetic variation (3n or more). Crossing over (
genetic recombination Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, ph ...
) and random segregation during
meiosis Meiosis (; , because it is a reductional division) is a special type of of in organisms used to produce the , such as or . It involves two rounds of division that ultimately result in four cells with only one copy of each (). Additionall ...

meiosis
can result in the production of new
allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is one of two, or more, forms of a given gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance ...
s or new combinations of alleles. Furthermore, random fertilization also contributes to variation. Variation and recombination can be facilitated by transposable genetic elements,
endogenous retrovirus Endogeny (biology), Endogenous Retrovirus, retroviruses (ERVs) are endogenous viral elements in the genome that closely resemble and can be derived from retroviruses. They are abundant in the genomes of Gnathostomata, jawed vertebrates, and they ...
es, LINEs, SINEs, etc. For a given genome of a multicellular organism, genetic variation may be acquired in somatic cells or inherited through the germline.


Forms

Genetic variation can be divided into different forms according to the size and type of genomic variation underpinning genetic change. Small-scale sequence variation (<1 kilobase, kb) includes
base-pair substitution A point mutation or substitution is a genetic mutation In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biolog ...
and
indels Indel is a molecular biology term for an insertion or deletion of bases in the genome of an organism. It is classified among small genetic variations, measuring from 1 to 10 000 base pairs in length, including insertion and deletion events that ...
. Large-scale
structural variation Genomic structural variation is the variation in structure of an organism's chromosome. It consists of many kinds of variation in the genome of one species, and usually includes microscopic and submicroscopic types, such as deletions, duplications, ...
(>1 kb) can be either
copy number variation Copy number variation (CNV) is a phenomenon in which sections of the genome are repeated and the number of repeats in the genome varies between individuals. Copy number variation is a type of structural variation: specifically, it is a type of Ge ...
(
loss Loss may refer to: Arts, entertainment, and media Music *Loss (Bass Communion album), ''Loss'' (Bass Communion album) (2006) *Loss (Mull Historical Society album), ''Loss'' (Mull Historical Society album) (2001) *"Losses", a song by Drake from ...
or
gain Gain or GAIN may refer to: Science and technology * Gain (electronics) In , gain is a measure of the ability of a (often an ) to increase the or of a from the input to the output port by adding energy converted from some to the signal. ...
), or
chromosomal rearrangement In genetics Genetics is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, ...
( translocation,
inversion Inversion or inversions may refer to: Arts * , a French gay magazine (1924/1925) * Inversion (artwork), ''Inversion'' (artwork), a 2005 temporary sculpture in Houston, Texas * Inversion (music), a term with various meanings in music theory and mus ...
, or Segmental acquired
uniparental disomy Uniparental disomy (UPD) occurs when a person receives two copies of a chromosome A chromosome is a long DNA molecule with part or all of the genome, genetic material of an organism. Most eukaryotic chromosomes include packaging proteins ca ...
). Genetic variation and recombination by transposable elements and endogenous retroviruses sometimes is supplemented by a variety of persistent viruses and their defectives which generate genetic novelty in host genomes. Numerical variation in whole
chromosome A chromosome is a long DNA molecule with part or all of the genome, genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones which, aided by Chaperone (protein), chaperone proteins, bind to and ...

chromosome
s or
genome In the fields of molecular biology Molecular biology is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, M ...

genome
s can be either
polyploidy Polyploidy is a condition in which the cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse ...
or
aneuploidy Aneuploidy is the presence of an abnormal number of chromosome A chromosome is a long DNA molecule with part or all of the genome, genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones whic ...
.


Maintenance in populations

A variety of factors maintain genetic variation in populations. Potentially harmful recessive alleles can be hidden from selection in the
heterozygous Zygosity (the noun, zygote, is from the Greek zygotos "yoked," from zygon "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an or ...
individuals in populations of
diploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chromosomes refer to the number of mate ...
organisms (recessive alleles are only expressed in the less common
homozygous Zygosity (the noun, zygote, is from the Greek zygotos "yoked," from zygon "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an or ...
individuals). Natural selection can also maintain genetic variation in balanced polymorphisms. Balanced polymorphisms may occur when heterozygotes are favored or when selection is frequency dependent.


RNA viruses

A high mutation rate caused by the lack of a proofreading mechanism appears to be a major source of the genetic variation that contributes to RNA virus evolution.Carrasco-Hernandez R et al. Are RNA Viruses Candidate Agents for the Next Global Pandemic? A Review. ILAR J. 2017 Dec 15;58(3):343-358. doi: 10.1093/ilar/ilx026. ; PMCID: PMC7108571. Genetic recombination also has been shown to play a key role in generating the genetic variation that underlies RNA virus evolution. Numerous RNA viruses are capable of
genetic recombination Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, ph ...
when at least two viral
genome In the fields of molecular biology Molecular biology is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, M ...

genome
s are present in the same host cell. RNA recombination appears to be a major driving force in determining genome architecture and the course of viral evolution among ''
Picornaviridae Picornaviruses are a group of related nonenveloped RNA virus An RNA virus is a virus A virus is a submicroscopic infectious agent that Viral replication, replicates only inside the living Cell (biology), cells of an organism. Virus ...

Picornaviridae
'' (
(+)ssRNA Baltimore classification is a system used to Virus classification, classify viruses based on their manner of messenger RNA (mRNA) synthesis. By organizing viruses based on their manner of mRNA production, it is possible to study viruses that behav ...
) (e.g.
poliovirus A poliovirus, the causative agent of polio Poliomyelitis, commonly shortened to polio, is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multi ...
). In the ''
Retroviridae A retrovirus is a type of virus that inserts a copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme ...

Retroviridae
'' ((+)ssRNA)(e.g.
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus ''Lentivirus'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, inc ...

HIV
), damage in the RNA genome appears to be avoided during
reverse transcription A reverse transcriptase (RT) is an enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substra ...
by strand switching, a form of genetic recombination. Recombination also occurs in the ''
Coronaviridae ''Coronaviridae'' is a family (biology), family of Viral envelope, enveloped, positive-strand RNA viruses which infect amphibians, birds, and mammals. The group includes the subfamilies ''Letovirinae'' and ''Orthocoronavirinae;'' the members of t ...
'' ((+)ssRNA) (e.g.
SARS Severe acute respiratory syndrome (SARS) is a viral respiratory disease Respiratory diseases, or lung diseases, are pathology, pathological conditions affecting the organs and tissues that make gas exchange difficult in Breathing, air-breathing ...
). Recombination in RNA viruses appears to be an adaptation for coping with genome damage. Recombination can occur infrequently between animal viruses of the same species but of divergent lineages. The resulting recombinant viruses may sometimes cause an outbreak of infection in humans.


History of genetic variation

Evolutionary biologists are often concerned with genetic variation, a term which in modern times has come to refer to differences in DNA sequences among individuals. However, quantifying and understanding genetic variation has been a central aim of those interested in understanding the varied life on earth since long before the sequencing of the first full genome, and even before the discovery of DNA as the molecule responsible for heredity. While today's definition of genetic variation relies on contemporary molecular genetics, the idea of heritable variation was of central importance to those interested in the substance and development of life even before the writings of Charles Darwin. The concept of heritable variation—the presence of innate differences between life forms that are passed from parents to offspring, especially within categories such as species—does not rely on modern ideas of genetics, which were unavailable to 18th- and 19th-century minds.


Pre-Darwinian concepts of heritable variation

In the mid-1700s,
Pierre Louis Maupertuis Pierre Louis Moreau de Maupertuis (; ; 1698 – 27 July 1759) was a French mathematician, philosopher and man of letters. He became the Director of the Académie des Sciences, and the first President of the Prussian Academy of Science, at the ...
, a French scholar now known primarily for his work in mathematics and physics, posited that while species have a true, original form, accidents during the development of nascent offspring could introduce variations that could accumulate over time. In his 1750 ''Essaie de Cosmologie'', he proposed that the species we see today are only a small fraction of the many variations produced by "a blind destiny," and that many of these variations did not "conform" to their needs, thus did not survive. In fact, some historians even suggest that his ideas anticipated the laws of inheritance further developed by
Gregor Mendel Gregor Johann Mendel (; cs, Řehoř Jan Mendel; 20 July 1822 – 6 January 1884) was a meteorologist, mathematician, biologist, AugustinianAugustinian may refer to: *Augustinians Augustinians are members of Christian religious orders th ...

Gregor Mendel
. Simultaneously, French philosopher
Denis Diderot Denis Diderot (; ; 5 October 171331 July 1784) was a French philosopher, art critic An art critic is a person who is specialized in analyzing, interpreting, and evaluating art Art is a diverse range of (products of) human activities ...

Denis Diderot
proposed a different framework for the generation of heritable variation. Diderot borrowed Maupertuis' idea that variation could be introduced during reproduction and the subsequent growth of offspring, and thought that production of a "normal" organism was no more probable than production of a "monstrous" one. However, Diderot also believed that matter itself had lifelike properties and could self-assemble into structures with the potential for life. Diderot's ideas on biological transformation, introduced in his 1749 work ''Letter on the Blind'', were thus focused on variability of spontaneously generated forms, not variability within existing species. Both Maupertuis and Diderot built on the ideas of Roman poet and philosopher
Lucretius Titus Lucretius Carus ( , ; 99 – c. 55 BC) was a Roman Roman or Romans most often refers to: *, the capital city of Italy *, Roman civilization from 8th century BC to 5th century AD *, the people of ancient Rome *', shortened to ''Rom ...
, who wrote in ''De rerum natura'' that all the universe was created by random chance, and only the beings that were not self-contradictory survived. Maupertuis' work is distinguished from the work of both Lucretius and Diderot in his use of the concept of conformity in explaining differential survival of beings, a new idea among those who believed that life changed over time. Like Diderot, two other influential minds of the 18th century—
Erasmus Darwin Erasmus Robert Darwin (12 December 173118 April 1802) was an English physician. One of the key thinkers of the Midlands Enlightenment, he was also a natural philosophy, natural philosopher, physiology, physiologist, Society for Effecting the ...
and
Jean-Baptiste Lamarck Jean-Baptiste Pierre Antoine de Monet, chevalier de Lamarck (1 August 1744 – 18 December 1829), often known simply as Lamarck (; ), was a French naturalist Natural history is a domain of inquiry involving organism In biology, ...

Jean-Baptiste Lamarck
—believed that only very simple organisms could be generated by spontaneous generation, so another mechanism was necessary to generate the great variability of complex life observed on earth. Erasmus Darwin proposed that changes acquired during an animal's life could be passed to its offspring, and that these changes seemed to be produced by the animal's endeavors to meet its basic needs. Similarly, Lamarck's theory of the variability among living things was rooted in patterns of use and disuse, which he believed led to heritable physiological changes. Both Erasmus Darwin and Lamarck believed that variation, whether it arose during development or during the animal's life, was heritable, a key step in theories of change over time extending from individuals to populations. In the subsequent century,
William Herschel Sir Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a spe ...

William Herschel
's telescopic observations of diverse nebulae across the night sky suggested to him that different nebulae could each be in different stages in the process of condensation. This idea, which came to be known as the
nebular hypothesis The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbiting t ...
, suggested that natural processes could both create order out of matter and introduce variation, and that these processes could be observed over time. While it may seem to the modern reader that astronomical theories are irrelevant to theories of organic variation, these ideas became significantly conflated with ideas of biological transformation—what we now know as evolution—in the mid-19th century, laying important groundwork for the work of subsequent thinkers such as Charles Darwin.


Darwin's concept of heritable variation

Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English naturalist Natural history is a domain of inquiry involving organism In biology, an organism () is any organic, life, living system that fu ...

Charles Darwin
's ideas of heritable variation were shaped by both his own scientific work and the ideas of his contemporaries and predecessors. Darwin ascribed heritable variation to many factors, but particularly emphasized environmental forces acting on the body. His theory of inheritance was rooted in the (now disproven) idea of - small, hypothetical particles, which capture the essence of an organism and travel from all over the body to the reproductive organs, from which they are passed to offspring. Darwin believed that the causal relationship between the environment and the body was so complex that the variation this relationship produced was inherently unpredictable. However, like Lamarck, he acknowledged that variability could also be introduced by patterns of use and disuse of organs. Darwin was fascinated by variation in both natural and domesticated populations, and his realization that individuals in a population exhibited seemingly purposeless variation was largely driven by his experiences working with animal breeders. Darwin believed that species changed gradually, through the accumulation of small, continuous variations, a concept that would remain hotly contested into the 20th century.


Post-Darwinian concepts of heritable variation

In the 20th century, a field that came to be known as
population genetics Population genetics is a subfield of that deals with genetic differences within and between s, and is a part of . Studies in this branch of examine such phenomena as , , and . Population genetics was a vital ingredient in the of the . Its pri ...
developed. This field seeks to understand and quantify genetic variation. The section below consists of a timeline of selected developments in population genetics, with a focus on methods for quantifying genetic variation. * 1866 - Heterozygosity: Gregor Mendel's hybridization experiments introduced the concept that in the 1950s came to be recognized as
heterozygosity Zygosity (the noun, zygote A zygote (from Greek ζυγωτός ''zygōtos'' "joined" or "yoked", from ζυγοῦν ''zygoun'' "to join" or "to yoke") is a eukaryotic cell formed by a fertilization event between two gamete A gamete ( /ˈ ...

heterozygosity
. In a
diploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chromosomes refer to the number of mate ...
species, one that contains two copies of DNA within each cell (one from each parent), an individual is said to be a heterozygote at a particular location in the genome if its two copies of DNA differ at that site. Heterozygosity, the average frequency of heterozygotes in a population, became a fundamental measure of the genetic variation in a population by the mid-20th century. If the heterozygosity of a population is zero, every individual is homozygous; that is, every individual has two copies of the same allele at the locus of interest and no genetic variation exists. * 1918 - Variance: In a seminal paper entitled "The correlation between relatives on the supposition of Mendelian inheritance", R.A. Fisher introduced the statistical concept of
variance In probability theory Probability theory is the branch of mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces ...

variance
; the average of squared deviations of a collection of observations from their mean (\sigma^2=\frac\sum_^I(x_i-\mu)^2), where \sigma^2 is the variance and \mu is the mean of the population from which the observations x_i are drawn). R.A. Fisher's work in population genetics was not just important to population genetics; these ideas would also form the foundations of modern statistics. * 1921 - Additive and dominant genetic variance: R.A. Fisher subsequently subdivided his general definition of variance into two components relevant to population genetics: additive and dominant genetic variance. An additive genetic model assumes that genes do not interact and that a trait value can be estimated simply by summing the effect of each gene on the trait. Under Fisher's model, the total genetic variance is the sum of the additive genetic variance (the variance in a trait due to these additive effects) and the dominant genetic variance (which accounts for interactions between genes). * 1948 - Entropy: Unlike variance, which was developed with the purpose of quantifying genetic variance, Claude Shannon's measure of diversity, now known as
Shannon entropy Shannon may refer to: * Shannon (given name) Shannon ("old river") is an Irish Irish most commonly refers to: * Someone or something of, from, or related to: ** Ireland, an island situated off the north-western coast of continental Europe ** Nor ...
, was developed as part of his work in communication theory as a way to quantify the amount of information contained in a message. However, the method quickly found use in population genetics, and was the central method used to quantify genetic diversity in a seminal paper by Richard Lewontin, "The Apportionment of Human Genetic Diversity." * 1951 - ''F-statistics:
F-statistics In population genetics, ''F''-statistics (also known as fixation indices) describe the statistically expected level of Zygosity, heterozygosity in a population; more specifically the expected degree of (usually) a reduction in heterozygosity when ...

F-statistics
, also known as fixation indices, were developed by population geneticist
Sewall Wright Sewall Green Wright FRS(For) Honorary FRSE Fellowship of the Royal Society of Edinburgh (FRSE) is an award granted to individuals that the Royal Society of Edinburgh, Scotland's national academy of science and Literature, letters, judged to ...

Sewall Wright
to quantify differences in genetic variation within and between populations. The most common of these statistics, FST, considers in its simplest definition two different versions of a gene, or alleles, and two populations that contain one or both of these two alleles. FST quantifies the genetic variability among these two populations by computing the average frequency of heterozygotes across the two populations relative to the frequency of heterozygotes if the two populations were pooled. F-statistics introduced the idea of quantifying hierarchical concepts of variance and would become the foundation of many important population genetic methods, including a set of methods that tests for evidence of natural selection in the genome.


See also

*
Genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species In biology, a species is the basic unit of biological classificati ...
*
Genetic variability Genetic variability is either the presence of, or the generation of, genetic differences. It is defined as "the formation of individuals differing in genotype The genotype of an organism is its complete set of genetic material. Genotype can also b ...
*
Human genetic variation Human genetic variation is the genetic differences in and among populations. There may be multiple variants of any given gene in the human population (alleles), a situation called Polymorphism (biology), polymorphism. No two humans are genetic ...

Human genetic variation


References


Further reading

* Mayr E. (1970): Populations, species, and evolution – An abridgment of Animal species and evolution. The Belknap Press of Harvard University Press, Cambridge, Massachusetts and London, England, . * Dobzhansky T. (1970): Genetics of the evolutionary process. Columbia, New York, . * McGinley, Mark; J. Emmett Duffy (ed). 2008.
Genetic variation
" In: ''Encyclopedia of Earth''. Washington, D.C.:
National Council for Science and the Environment The National Council for Science and the Environment (NCSE) is a U.S.-based nonpartisan, non-profit organization which has a mission to improve the scientific basis of Natural environment, environmental decision-making. NCSE was founded in 1990. In ...
.
"Genetic Variation"
in Griffiths, A.J.F. ''Modern Genetic Analysis, Vol 2.'', p. 7
"How is Genetic Variation Maintained in Populations"
in Sadava, D. et al. ''Life: The Science of Biology'', p. 456 * Nevo, E.; Beiles, A.
Genetic variation in nature
.
Scholarpedia ''Scholarpedia'' is an English-language wiki-based online encyclopedia with features commonly associated with Open access (publishing), open-access online academic journals, which aims to have quality content. ''Scholarpedia'' articles are writt ...
, 6(7):8821. doi:10.4249/scholarpedia.8821 * Hedrick P. (2011): Genetics of populations. Jones & Bartlett Learning, . *Albers P. K. and McVean G. (2018)
Dating genomic variants and shared ancestry in population-scale sequencing data
''bioRxiv'': 416610.
doi #REDIRECT DOI DOI or Doi may refer to: Science and technology * Digital object identifier, an international standard for document identification * Distinctness of image, a quantification of vision used in optics * 2,5-Dimethoxy-4-iodoamphetamine, a ...
: 10.1101/416610. * Rieger R. Michaelis A., Green M. M. (1976): Glossary of genetics and cytogenetics: Classical and molecular. Springer-Verlag, Heidelberg - New York, ; . * Griffiths, A. J. F. (1999). An Introduction to genetic analysis. W. H. Freeman, San Francisco, . * Cavalli-Sforza L. L., Bodmer W. F. (1999): ''The genetics of human populations''. Dover, Mineola, New York, .


External links


Genetic variation
{{DEFAULTSORT:Genetic Variation Population genetics