BIOL 1108 Lecture Notes - Lecture 4: Genetic Drift, Founder Effect, Population Bottleneck

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30 Jan 2017
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Core concept 5: migration, mutation, genetic drift, and non-random mating are nonadaptive mechanisms of evolution. Other factors besides natural selection that cause changes in allele frequencies: migration, mutation, genetic drift. Evolutionary mechanisms each have different consequences for the population: causes of microevolution (shift in trait/allele frequency) involve relaxing the assumptions of the hw equilibrium. Natural selection: small population instead of large. Small populations have trouble with drift (random change in allele availability) because random events have disproportionately heavy impact. Losing 10 out of 20 is hard, but 10 out of 200 not so much: genetic drift a random change in an allele frequency due to some outside change. Affects all population sizes, random event but expected (stochasticity) Small populations have fewer individuals to reproduce. Not all allele combinations reproduce in any given breeding. This leads to the loss (or gain) of random alleles and therefore a decrease (or an increase) in genetic variability.

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