Neutral rates, GC and CpG content. Scatter plots of (a) human-macaque JC neutral substitution rates against GC content, for CpG sites (triangles), non-CpG sites (circles), and 'union' sites (crosses), and (b) fraction of CpG sites against GC content. Each point represents one of 2,270 windows of size 1 Mb. Lowess smoothers are superimposed to the plots to help visualize the relationships. Note the different scales on the truncated y-axis for (a).