Figure 2
Ratios of replacement to silent polymorphism (P n /P s ) in S. cerevisiae, and substitutions (D n /D s ) between S. cerevisiae and S. paradoxus. Results were obtained by pooling polymorphism and divergence data for multiple genes within each expression category (see Fig. S1 for similar results using a different approach). P n /P s ratios are lower in highly expressed genes: upper vs. lower 50% with singletons, P = 0.172; upper vs. lower 25% with singletons, P = 0.026; upper vs. lower 50% without singletons, P = 0.203; upper vs. lower 25% without singletons, P = 0.023. D n /D s ratios are lower for highly expressed genes for all comparisons (P < 0.0001).