Evolution of the mouse sperm methylome. Chromosomal distributions of DMRs between M. m. musculus and M. spretus. The observed and expected numbers of DMRs are plotted to the left. Expectations are based on the proportion of CpG sites on each chromosome multiplied by the total number of DMRs. Darkly shaded chromosomes have significantly more or less DMRs than expected based on chromosome-wise hypergeometric tests. The X chromosome has significantly fewer DMRs compared to all of the autosomes (P < 0.001).