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Population bottleneck followed by recovery or extinction. A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide, speciocide, widespread violence or intentional culling.
Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, [1] is the change in the frequency of an existing gene variant in a population due to random chance. [ 2 ] Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation . [ 3 ]
As of 2016, the selective pressure for the high gene prevalence of CF mutations is still uncertain, and may be due to an unbiased genetic drift rather than a selective advantage. Approximately one in 25 persons of European descent is a carrier of the disease, and one in 2500 to 3000 children born is affected by Cystic fibrosis.
Fixation rates can easily be modeled as well to see how long it takes for a gene to become fixed with varying population sizes and generations. For example, The Biology Project Genetic Drift Simulation allows to model genetic drift and see how quickly the gene for worm color goes to fixation in terms of generations for different population sizes.
Evolution is the change in the heritable characteristics of biological populations over successive generations. [1] [2] It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. [3]
A highly indicative test of changes in allele frequencies is the QTL sign test, and other tests include the Ka/Ks ratio test and the relative rate test. The QTL sign test compares the number of antagonistic QTL to a neutral model, and allows for testing of directional selection against genetic drift. [11]
Genetic variation Genetic variation of Eurasian populations showing different frequency of West- and East-Eurasian components [56] It is commonly assumed that early humans left Africa, and thus must have passed through a population bottleneck before their African-Eurasian divergence around 100,000 years ago (ca. 3,000 generations).
Population genetics is the branch of biology that provides the mathematical structure for the study of the process of microevolution. Ecological genetics concerns itself with observing microevolution in the wild. Typically, observable instances of evolution are examples of microevolution; for example, bacterial strains that have antibiotic ...