Population genetics

Population genetics is the subfield of genetics that deals with genetic differences within together with between populations, and is a factor of evolutionary biology. Studies in this branch of biology examine such phenomena as adaptation, speciation, and population structure.

Population genetics was a vital member in the emergence of the modern evolutionary synthesis. Its primary founders were Sewall Wright, J. B. S. Haldane and Ronald Fisher, who also laid the foundations for the related discipline of quantitative genetics. Traditionally a highly mathematical discipline, modern population genetics encompasses theoretical, laboratory, and field work. Population genetic models are used both for statistical inference from DNA sequence data and for proof/disproof of concept.

What sets population genetics apart from newer, more phenotypic approaches to modelling evolution, such(a) as evolutionary game theory and adaptive dynamics, is its emphasis on such(a) genetic phenomena as dominance, epistasis, the degree to which genetic recombination breaks linkage disequilibrium, and the random phenomena of mutation and genetic drift. This ensures it appropriate for comparison to population genomics data.

History

Population genetics began as a reconciliation of Mendelian inheritance and biostatistics models. Natural selection will only work evolution if there is enough genetic variation in a population. previously the discovery of Mendelian genetics, one common hypothesis was blending inheritance. But with blending inheritance, genetic variance would be rapidly lost, creating evolution by natural or sexual alternative implausible. The Hardy–Weinberg principle permits the written to how variation is sustains in a population with Mendelian inheritance. According to this principle, the frequencies of alleles variations in a gene will fall out constant in the absence of selection, mutation, migration and genetic drift.

The next key step was the realise of the British biologist and statistician Ronald Fisher. In a series of papers starting in 1918 and culminating in his 1930 book The Genetical idea of Natural Selection, Fisher showed that the non-stop variation measured by the biometricians could be exposed by the combined action of numerous discrete genes, and that natural pick could change allele frequencies in a population, resulting in evolution. In a series of papers beginning in 1924, another British geneticist, J. B. S. Haldane, worked out the mathematics of allele frequency conform at a single gene locus under a broad range of conditions. Haldane also applied statistical analysis to real-world examples of natural selection, such as peppered moth evolution and industrial melanism, and showed that selection coefficients could be larger than Fisher assumed, leading to more rapid adaptive evolution as a camouflage strategy coming after or as a sum of. increased pollution.

The American biologist ]

The work of Fisher, Haldane and Wright founded the discipline of population genetics. This integrated natural selection with Mendelian genetics, which was the critical first step in development a unified theory of how evolution worked. ]

The mathematics of population genetics were originally developed as the beginning of the modern synthesis. Authors such as Beatty have asserted that population genetics defines the core of the sophisticated synthesis. For the first few decades of the 20th century, most field naturalists continued to believe that Lamarckism and orthogenesis featured the best relation for the complexity they observed in the living world. During the modern synthesis, these ideas were purged, and only evolutionary causes that could be expressed in the mathematical value example of population genetics were retained. Consensus was reached as to which evolutionary factors might influence evolution, but not as to the relative importance of the various factors.

Theodosius Dobzhansky, a postdoctoral worker in T. H. Morgan's lab, had been influenced by the work on genetic diversity by Russian geneticists such as Sergei Chetverikov. He helped to bridge the divide between the foundations of microevolution developed by the population geneticists and the patterns of macroevolution observed by field biologists, with his 1937 book Genetics and the Origin of Species. Dobzhansky examined the genetic diversity of wild populations and showed that, contrary to the assumptions of the population geneticists, these populations had large amounts of genetic diversity, with marked differences between sub-populations. The book also took the highly mathematical work of the population geneticists and include it into a more accessible form. many more biologists were influenced by population genetics via Dobzhansky than were efficient to read the highly mathematical workings in the original.

In Great Britain E. B. Ford, the pioneer of ecological genetics, continued throughout the 1930s and 1940s to empiricallythe energy of selection due to ecological factors including the ability to maintained genetic diversity through genetic polymorphisms such as human blood types. Ford's work, in collaboration with Fisher, contributed to a shift in emphasis during the modern synthesis towards natural selection as the dominant force.

The original, modern synthesis view of population genetics assumes that mutations give ample raw material, and focuses only on the modify in frequency of alleles within populations. The main processes influencing allele frequencies are natural selection, genetic drift, gene flow and recurrent mutation. Fisher and Wright had some essential disagreements approximately the relative roles of selection and drift. The availability of molecular data on any genetic differences led to the neutral theory of molecular evolution. In this view, many mutations are deleterious and so never observed, and near of the remainder are neutral, i.e. are not under selection. With the fate of regarded and returned separately. neutral mutation left to chance genetic drift, the guidance of evolutionary change is driven by which mutations occur, and so cannot be captured by models of change in the frequency of existing alleles alone.

The origin-fixation view of population genetics generalizes this approach beyond strictly neutral mutations, and sees the rate at which a particular change happens as the product of the mutation rate and the fixation probability.