Distribution of M:F ratios and average expression levels of Z-linked genes. (a) The distribution of M:F ratio (Y axis) as a function of position on Z chromosome (X axis). Zp arm, Zq arm, centromere and MHM region of Z chromosome are indicated. (b) The percentile distribution (Y axis) of Z genes as a function of ratio values (X axis, log2 scale). (c) The trend of M:F ratio distribution is represented as running averages of 30 consecutive ratios positioned at the median position of the 30 ratios. (d) The average expression level (Y axis, log2 scale) of all expressed Z genes (Z), compensated Z genes (Compensated) and non-compensated Z genes along with autosomal genes in females and males.