FIG. 2.—

Divergent sequences are significantly W→S biased in many, but not all, eukaryotes. Genomic regions with a high divergence show a significant enrichment for W→S substitutions (BDS) compared with regions with fewer substitutions. BDS is found in human (A), mouse, dog (B), stickleback, fly, and worm (C). In contrast, chicken and yeast (D) do not exhibit significant W→S BDS. These patterns are not sensitive to the size of the window (500–2000 bp) or the substitution density threshold. The gray bars indicate 95% confidence intervals for the BDS score. This figure includes substitution densities for which between 1% and 99% of substitutions are considered divergent. Table 1 gives BDS statistics for all species considered, and plots are provided for the other four species in supplementary figure S1 (Supplementary Material online).