The population genetics of the branch which is genetics , the heredity processes within biological populations studied. It determines the relative frequency of homologous genes ( alleles ) in populations ( gene frequency ) and researches their change under the influence of mutation , selection , random gene drift , the separation of subpopulations and the gene flow between populations. It is of great importance in evolutionary research as well as in animal and plant breeding .
An important principle of population genetics is the Hardy-Weinberg law , independently discovered by Wilhelm Weinberg and Godfrey Harold Hardy in 1908 , which describes a state of equilibrium in which the frequency of the alleles of a gene from generation to generation in the case of purely random mating and in the absence of any selection remains constant.
Population genetics established itself as an independent branch of research in the 1920s, after Reginald Punnett introduced the previously neglected discovery of Weinberg and Hardy's as "Hardy's law" into population biology in 1917 . The founders of this new branch of research were Sewall Wright , Ronald A. Fisher and JBS Haldane . In the 1930s and 1940s, population genetics made a significant contribution to the unification of the evolution theory founded by Charles Darwin with the genetics linked to Gregor Mendel in the synthetic evolution theory , which is still valid today , by helping to resolve existing contradictions between these theories.
The Hardy-Weinberg equilibrium is a theoretical construct that does not correspond to any real population. In real populations, there are various mechanisms of selection that favor certain alleles over others. Except in very small populations, however, this does not lead to the only remaining “ fittest ” genotype , but rather a certain diversity ( polymorphism ) is always retained. The numerous reasons for this are also the subject of population genetic research. One of them is the frequently observed phenomenon of heterosis , which consists in the fact that mixed-breed ( heterozygous ) individuals are preferred by the selection to pure- breed ( homozygous ), i.e. they prove to be fitter. In the opposite case, inbreeding , i.e. the mating of genetically closely related or identical individuals, proves to be disadvantageous, which is particularly due to the increased occurrence of recessive genes.
- John H. Gillespie: Population Genetics: A Concise Guide , Johns Hopkins Press, 2nd ed. 2004, ISBN 0-8018-5755-4
- Matthew Hamilton: Population Genetics , John Wiley & Sons 2009
- Daniel L. Hartl & Andrew G. Clark: Principles of Population Genetics , Palgrave Macmillan, 4th ed. 2007, ISBN 0-87893-306-9
- Philip W. Hedrick: Genetics of Populations , Jones & Bartlett Publ., 4th ed. 2009
- Entry in Edward N. Zalta (Ed.): Stanford Encyclopedia of Philosophy .
- Working material, calculations on population genetics ( Memento from September 27, 2007 in the Internet Archive ) (PDF file; 401 kB)