Population genetics 219268 225343368 2008-07-13T05:06:08Z Ben Tillman 623782 +template {{evolution3}} '''Population genetics''' is the study of the [[allele frequency]] distribution and change under the influence of the four evolutionary forces: [[natural selection]], [[genetic drift]], [[mutation]] and [[gene flow]]. It also takes account of population subdivision and population structure in space. As such, it attempts to explain such phenomena as [[Adaptation (biology)|adaptation]] and [[speciation]]. Population genetics was a vital ingredient in the [[modern evolutionary synthesis]], its primary founders were [[Sewall Wright]], [[J. B. S. Haldane]] and [[Ronald Fisher|R. A. Fisher]], who also laid the foundations for the related discipline of [[quantitative genetics]]. == Scope and theoretical considerations == Perhaps the most significant "formal" achievement of the [[modern evolutionary synthesis]] has been the framework of mathematical population genetics. Indeed some authors (Beatty 1986) would argue that it does ''define'' the core of the modern synthesis. [[Richard Lewontin|Lewontin]] (1974) outlined the theoretical task for population genetics. He imagined two spaces: a "genotypic space" and a "phenotypic space". The challenge of a ''complete'' theory of population genetics is to provide a set of laws that predictably map a population of [[genotype]]s (''G''<sub>1</sub>) to a [[phenotype]] space (''P''<sub>1</sub>), where [[natural selection|selection]] takes place, and another set of laws that map the resulting population (''P''<sub>2</sub>) back to genotype space (''G''<sub>2</sub>) where [[Mendelism|Mendelian]] genetics can predict the next generation of genotypes, thus completing the cycle. Even leaving aside for the moment the non-Mendelian aspects revealed by [[molecular genetics]], this is clearly a gargantuan task. Visualizing this transformation schematically: :<math>G_1 \; \stackrel{T_1}{\rightarrow} \; P_1 \; \stackrel{T_2}{\rightarrow} \; P_2 \; \stackrel{T_3}{\rightarrow} \; G_2 \; \stackrel{T_4}{\rightarrow} \; G_1' \; \rightarrow \cdots</math> (adapted from Lewontin 1974, p. 12). XD ''T''<sub>1</sub> represents the genetic and [[epigenetic]] laws, the aspects of functional biology, or [[developmental biology|development]], that transform a genotype into phenotype. We will refer to this as the "[[genotype-phenotype map]]". ''T''<sub>2</sub> is the transformation due to natural selection, ''T''<sub>3</sub> are epigenetic relations that predict genotypes based on the selected phenotypes and finally ''T''<sub>4</sub> the rules of Mendelian genetics. In practice, there are two bodies of evolutionary theory that exist in parallel, traditional population genetics operating in the genotype space and the [[biometry|biometric]] theory used in [[plant breeding|plant]] and [[animal breeding]], operating in phenotype space. The missing part is the mapping between the genotype and phenotype space. This leads to a "sleight of hand" (as Lewontin terms it) whereby variables in the equations of one domain, are considered parameters or ''constants'', where, in a full-treatment they would be transformed themselves by the evolutionary process and are in reality ''functions'' of the state variables in the other domain. The "sleight of hand" is assuming that we know this mapping. Proceeding as if we do understand it is enough to analyze many cases of interest. For example, if the phenotype is almost one-to-one with genotype ([[sickle-cell disease]]) or the time-scale is sufficiently short, the "constants" can be treated as such; however, there are many situations where it is inaccurate. == Population geneticists == The three founders of population genetics were the Britons [[Ronald Fisher|R.A. Fisher]] and [[J.B.S. Haldane]] and the American [[Sewall Wright]]. Fisher and Wright had some fundamental disagreements and a controversy about the relative roles of selection and drift continued for much of the century between the Americans and the British. The Frenchman [[Gustave Malécot]] was also important early in the development of the discipline. [[John Maynard Smith]] was Haldane's pupil, whilst [[W.D. Hamilton]] was heavily influenced by the writings of Fisher. The American [[George R. Price]] worked with both Hamilton and Maynard Smith. On the American side, [[Richard Lewontin]] and the Japanese [[Motoo Kimura]] were heavily influenced by Wright. ==See also== {{columns-list|3| * [[Coalescent theory]] * [[Dual inheritance theory]] * [[Ecological genetics]] * [[Ewens's sampling formula]] * [[Fitness landscape]] * [[Founder effect]] * [[Genetic diversity]] * [[Genetic drift]] * [[Genetic erosion]] * [[Genetic pollution]] * [[Gene pool]] * [[Genotype-phenotype distinction]] * [[Habitat fragmentation]] * [[Hardy-Weinberg principle]] * [[Microevolution]] * [[Molecular evolution]] * [[Muller's ratchet]] * [[Mutational meltdown]] * [[Panmictic|Panmixia]] * [[Population bottleneck]] * [[Quantitative genetics]] * [[Selection]] * [[Small population size]] * [[Viral quasispecies]]}} ==References== *J. Beatty. "The synthesis and the synthetic theory" in Integrating Scientific Disciplines, edited by W. Bechtel and Nijhoff. Dordrecht, 1986. * [[Luigi Luca Cavalli-Sforza]]. Genes, Peoples, and Languages. North Point Press, 2000. * [[Luigi Luca Cavalli-Sforza]] et al. The History and Geography of Human Genes. Princeton University Press, 1994. * [[James F. Crow]] and [[Motoo Kimura]]. Introduction to Population Genetics Theory. Harper & Row, 1972. * [[Warren Ewens|Warren J Ewens]]. Mathematical Population Genetics. Springer-Verlag New York, Inc., 2004. ISBN 0-387-20191-2 * [[John H. Gillespie]] Population Genetics: A Concise Guide, Johns Hopkins Press, 1998. ISBN 0-8018-5755-4. * Richard Halliburton. Introduction to Population Genetics. Prentice Hall, 2004 * Daniel Hartl. Primer of Population Genetics, 3rd edition. Sinauer, 2000. ISBN 0-87893-304-2 * Daniel Hartl and Andrew Clark. Principles of Population Genetics, 3rd edition. Sinauer, 1997. ISBN 0-87893-306-9. * [[Richard Lewontin|Richard C. Lewontin]]. The Genetic Basis of Evolutionary Change. Columbia University Press, 1974. * [[William B. Provine]]. The Origins of Theoretical Population Genetics. University of Chicago Press. 1971. ISBN 0-226-68464-4. * [[Spencer Wells]]. The Journey of Man. Random House, 2002. * [[Spencer Wells]]. Deep Ancestry: Inside the Genographic Project. National Geographic Society, 2006. * {{cite journal |last=Cheung|first=KH |coauthors=Osier MV, Kidd JR, Pakstis AJ, Miller PL, Kidd KK |title=ALFRED: an allele frequency database for diverse populations and DNA polymorphisms |journal=Nucleic Acids Research |volume=28 |issue=1 |year=2000 |pages=361–3 |doi=10.1093/nar/28.1.361 |pmid=10592274 }} == External links == *[http://alfred.med.yale.edu/alfred/ ALFRED database] *[http://www.esp.org/books/sturt/history/contents/sturt-history-ch-17.pdf History of population genetics] * National Geographic: [https://www5.nationalgeographic.com/genographic/atlas.html Atlas of the Human Journey] ([[Haplogroup]]-based human migration maps) *[http://vlab.infotech.monash.edu.au/simulations/cellular-automata/population-genetics/ Monash Virtual Laboratory] - Simulations of habitat fragmentation and population genetics online at Monash University's Virtual Laboratory. * [http://www.familytreedna.com/public/Nordic-Celtic/ Nordic and Celtic DNA Project] (Saami & Iberian). {{popgen}} {{genetics-footer}} {{evolution}} [[Category:Population genetics|*]] [[Category:Evolutionary biology]] [[Category:Statistical genetics]] [[bg:Популационна генетика]] [[ca:Genètica de poblacions]] [[de:Populationsgenetik]] [[es:Genética de poblaciones]] [[fr:Génétique des populations]] [[ko:집단유전학]] [[it:Genetica delle popolazioni]] [[he:גנטיקה של אוכלוסיות]] [[la:Genetica populationis]] [[hu:Populációgenetika]] [[nl:Populatiegenetica]] [[ja:集団遺伝学]] [[pl:Genetyka populacyjna]] [[pt:Genética populacional]] [[ru:Популяционная генетика]] [[sr:Популациона генетика]] [[fi:Populaatiogenetiikka]] [[sv:Populationsgenetik]] [[tr:Popülasyon genetiği]] [[zh:群体遗传学]]