Fig. 1.

Dosage compensation patterns across species. Increased transcription of the X chromosome is required for dosage compensation in Mus musculus (mouse), Caenorhabditis elegans (worm), and Drosophila melanogaster (fly). In the mouse, one X chromosome is upregulated in both sexes. A second step of regulation takes place in which one X chromosome is randomly inactivated in mouse females. In the worm, the X chromosome is upregulated in males, and both X chromosomes are downregulated by half in hermaphrodite females. In the fly, only in males the X chromosome is upregulated