February_6_2013_NKW

population size does not affect the rate of neutral

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Unformatted text preview: uot; •  Affected by linkage of mutant allele to other chromosomal regions under selection" Most evolution at the " molecular level is " neutral with " respect to fitness. " " " Population size does " not affect the " rate of neutral " changes. " " Many changes are " slightly deleterious " & are fixed by chance, " despite negative" selection. " " The rate of such " changes is higher " in small populations. " " 2 Purifying selection is the most common (most mutations are deleterious)" New Mutations Selective Sieve More effective with large N and large |s| Less effective with small N and small |s| Substitutions in lineage 3 Distribution of selective coefficients of new mutations (?) High frequency of slightly deleterious mutations Human ­chimp sequence divergence on different chromosomes largely non ­coding Completely neutral mutations probably common Beneficial mutations rare 1.  What is the best explana1on for the differences on X and Y compared to autosomes?...
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