Fig. 4.

X-biased gene expression across the sex chromosomes. X chromosome and Y chromosome SNPs were identified to quantify allele-specific gene expression on the sex chromosomes. Genes are expressed at higher levels on the X chromosome as compared with the Y chromosome in both stratum 2 (N = 414 genes) and among the genes that retain coding sequence on the Y chromosome in stratum 1 (N = 52 genes). Medians that are significantly greater than an equal X to Y expression ratio are shown in green (one-sample Mann–Whitney U test, mu = 0, corrected for multiple comparisons). Whiskers are 1.5× the interquartile range. Outliers are not shown.