Figure 3.

ZZ male and ZW female expression levels as a function of M:F ratio. Graphs show the median expression level of genes as a function of M:F ratio. For each tissue, all genes showing expression from the Z chromosome or from autosomes 1-5 were grouped into bins according to M:F ratio. The graphs indicate that autosomal genes with high (>1.2) or low (<0.8) M:F ratios show generally lower expression, in both sexes, relative to genes that are equally expressed in the two sexes (M:F ratio near 1), indicating that sexually dimorphic expression is not associated with higher expression in one sex relative to the majority of genes. Among Z genes, expression in females varies little as M:F ratio changes. Male genes, however, are expressed significantly lower at low M:F ratios near 1, relative to higher M:F ratios. Bin width is 0.2. Values are plotted at the mid-point of the bin. A small number of genes, with M:F ratios outside of the range shown, are included in the most extreme bins.