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The relationship between the sequence identity of the closest homolog and the ratio of non-synonymous to synonymous human SNPs per site (Ka/Ks).
The Ka/Ks ratio was averaged for genes within each sequence identity bin. The ratio is shown for all (black) and only for validated (red) SNPs from the dbSNP database . Above 60% sequence identity, the Ka/Ks ratio increases monotonically as the homolog sequence identity increases.