Dosage Compensation Mechanisms: Evolution

Degeneration of sex-limited chromosomes generates the need for dosage compensation mechanisms able to equalize in both sexes the amount of products derived from sex-linked genes. Evolution of these mechanisms is understood in some detail in the fly Drosophila melanogaster, the nematode Caenorhabditis elegans and in eutherian mammals. Dosage Compensation Mechanisms: An Evolutionary Perspective In many species, sex chromosomes that originated as an identical, homologous pair currently show mor-phological differentiation in one of the sexes. An individual of the homogametic sex has two identical sex chromosomes, whereas an individual of the heterogametic sex has two distinct chromosomes. The chromosome restricted to the heterogametic sex often has a low number of genes. Loss of gene function is caused by the combined effect of chromosom