Does gene dosage really matter?

Abstract

Mechanisms to compensate for dosage differences of genes on sex chromosomes are widespread in animals and have been thought to be critical for viability. However, in birds, compensation is inefficient, implying that for many genes dosage compensation is not critical, and for some genes, dosage differences have even been selected for.

Figure 1

Regulation of gene expression on sex chromosomes relative to autosomes in males (M) and females (F) of mammals and Drosophila (XX female:XY male), and birds (ZW female:ZZ male). Basal autosome-equivalent expression level is in light blue; upregulated regions are represented in dark blue and inactivated regions in white. Genes on the two Z chromosomes of the male bird are presumed to have equal expression to the autosomes, but the single Z of female birds is only partially dosage compensated (orange shading represents a mixture of genes compensated to various degrees). The heterochromatic and largely inactive or specialized Y and W chromosomes are represented in yellow.