Fig. 7

Conserved patterns of reduced variation in gene expression at primitive streak. We plotted the P value distributions of F tests of the null hypothesis that there is no reduction in variation in gene expression levels as samples progress along the time course in human (a) and chimpanzee (b) samples. \( \widehat{\uppi} \)₀ is the estimated proportion of null tests in each distribution. In the next four panels, we plotted the P value distribution for the same test, but included only genes whose variation was classified as reduced between states in the other species; thus in (c) we plotted P value distributions of F tests in chimpanzees only for genes who variation was classified as reduced (P < 0.05) in humans and in (d) we did the reverse. In (e) (chimpanzee conditional on human) and (f) (human conditional on chimpanzee), we plotted the P value distributions of F tests of the null hypothesis that there is increase in variation in gene expression levels as the samples progress from day 1 to 2