Relationship between sex bias in gene expression and expression level. Relationship of male-to-female ratios (m:f) with male (white) and female (gray) expression levels. While male expression is significantly higher for genes with high m:f ratio (m[ale]-biased) the opposite is indicated for genes expressed in females. Genes with a low m:f ratio (f[emale]-biased) are slightly more expressed in females. Asterisks indicate standard Type I error thresholds. Boxes include the 2nd and 3rd quantile; whiskers extend to the most extreme data points that lie within 1.5 times the interquartile range from the box; points depict extreme values beyond that boundary.