BRCA1 evolution in the human, bonobo, and chimpanzee clade. A. dN/dS values for BRCA1 were calculated on each branch of the primate tree using the free-ratio model in PAML. dN/dS values > 1 are shown in bold italics. The numbers of non-synonymous (N) and synonymous (S) substitutions predicted to have occurred along each branch are indicated in parentheses (N:S). The asterisk represents the last common ancestor of humans, bonobos, and chimpanzees. MYA, million years ago. B. The number of human-specific non-synonymous (N) and synonymous (S) substitutions in BRCA1 and other genes encoding BRCA1-interacting proteins. The length of each gene is shown in kilobases (kb). Non-synonymous and synonymous substitutions are shown as number of substitutions per kilobases (N/kb and S/kb, respectively). An “enrichment ratio” of N/kb over S/kb was also calculated. C. A domain diagram of BRCA1 is shown with the RING domain, coiled-coil domain (C-C), and BRCT domains indicated. On this are superimposed all of the non-synonymous substitutions predicted to have occurred in the tree shown in panel A since the divergence of humans, bonobos, and chimpanzees from their last common ancestor (asterisk in A). Vertical lines indicate substitutions specific to humans, lines with white circles are substitutions specific to bonobos, and lines with grey circles are substitutions specific to chimpanzees. Lines with black circles indicate substitutions common to both bonobos and chimpanzees.