Prevalence of positive selection among nearly neutral amino acid replacements in Drosophila.

摘要: Abstract We have estimated the selective effects of amino acid replacements in natural populations by comparing levels polymorphism 91 genes African Drosophila melanogaster with their divergence from simulans. The include about equal numbers whose level expression adults is greater males, females, or approximately sexes. Markov chain Monte Carlo methods were used to sample key parameters stationary distribution and a model which effect each nonsynonymous mutation regarded as random some underlying normal mean may differ one gene next. Our analysis suggests that ≈95% all mutations could contribute are deleterious, average proportion deleterious polymorphisms samples ≈70%. On other hand, fixed differences between species positively selected, although scaled selection coefficient (Nes) very small. We estimate ≈46% Nes < 2, ≈84% 4, ≈99% 7. Although positive among seems pervasive, most be nearly neutral. There significant sex-biased unbiased genes, relate primarily distributions mutational fraction slightly weakly beneficial fixed. McDonald–Kreitman test polymorphism divergence protein evolution