Figure 3. Dn/ds distribution for chimp (a), dog (b) and mice (c) for the probe sets interrogated by the HG-U133plus2 arrays.

Positive selection signature can be observed in the chimp on the right side of the histogram. (d) Comparison of dn/ds for the chimp between embryo/oocyte specific and adult tissue specific probes. Testing the difference between the distributions with a nonparametric (Mann-Whitney) test yields a median shift of about 15% with a two-tailed significance p-value 10e−16.