Male-to-female ratio of gene expression for autosomal and Z-linked genes. Best Gaussian kernel density function for log2(m:f) ratios of 3300 autosomal genes (black) and 156 Z-linked genes (red). A mean logarithmic male-to-female ratio (log2(m:f) of zero indicates that autosomal genes are equally expressed between females and males (black dotted line). Expression of Z-linked genes, on the contrary, is on average male biased (red dotted line) and indicates a lack of dosage compensation for most genes. The shape of the kernel is robust to different smoothing kernels and parameter settings.