Bayesian Analysis Suggests that Most Amino Acid Replacements in Drosophila Are Driven by Positive Selection

摘要: One of the principal goals population genetics is to understand processes by which genetic variation within species (polymorphism) becomes converted into differences between (divergence). In this transformation, selective neutrality, near and positive selection may each play a role, differing from one gene next. Synonymous nucleotide sites are often used as uniform standard comparison across genes on grounds that synonymous subject relatively weak constraints so may, first approximation, be regarded neutral. also interdigitated with nonsynonymous affected equally genomic context demographic factors. Hence levels polymorphism divergence amino acid replacement in potentially informative about magnitude forces associated replacements. We have analyzed 56 data D. simulans compared reference strain melanogaster. The framework analysis Bayesian assumes distribution effects (Malthusian fitnesses) Gaussian mean differs for gene. such model, average scaled intensity (γ =N e s) replacements eligible become polymorphic or fixed −7.31, deviation locus 6.79 (assuming homoscedasticity loci). For newly arising mutations type occur autosomal X-linked genes, proportion beneficial 19.7%. Among polymorphisms sample, expected 47.7%, among 94.3%. +5.1. presence pervasive single exception kl-5, Y-linked fertility find no evidence significant fraction neutral nearly drives at only subset loci. These results model dependent we discuss possible modifications might allow more fixed.