Multicopy genes show evidence of altered selective pressures on amino acid sequence during recent primate evolution.

<p>Density plots showing the distribution of dN/dS ratios for multicopy genes (<i>green</i>) compared to all RefSeq genes (<i>red</i>) for human versus chimpanzee. There is a significant enrichment for elevated rates of non-synonymous substitution in multicopy genes versus the genome average (p = 3.3×10⁻⁷, Kolmogorov-Smirnov test). This excess of non-synonymous amino-acid changes in recent primate evolution at multicopy genes is consistent with either reduced selective constraint and/or selection for proteins with altered function. Similar results are obtained when comparing human with orangutan and macaque (<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004418#pgen.1004418.s005" target="_blank">Figure S5</a>).