EEB 390 Lecture Notes - Lecture 7: Small Population Size, Allele Frequency, Effective Population Size
9 Oct 2020
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Document Summary
Review: where are we, we added a model (wright-fisher, small population size can lower variation with the tendency for alleles to be lost and/or go to xation. Lose heterozygosity as a result of small population: understand effective population size and its relation to census size, coalescence. Two important elements are: effective population size, strength of selection (measured by selection coef cient, s) Selection needs to be bigger than 1/2ne for selection to dominate s > Larger e ective population size the less strong selection has to be to overcome drift. Big effective population (100,000) and small selection (s = 0. 005: population is slowly increasing of p and decreasing frequency of q, eventually becoming x. Big effective population (100,000) and medium selection (s = 0. 05: much more quickly p goes towards xation. Big effective population (100,000) and strong selection (s = 0. 5: very quickly p goes towards xation.
