Fig. 3.

Dosage compensation in males (XY), females (XX), and metafemales (XXX). If gene dosage effects in the various genotypes are set to the gene copy relationship (horizontal axis percentage) and inverse dosage effects on each X chromosome (designated percentages in boxes) are set to 100% in normal diploid females (XX), the total expression of X chromosomes will be 200%. Once one X chromosome is lost over evolutionary time in males, the gene dosage effects will be at 50%, whereas the inverse dosage effects produced by this monosomic X chromosome will be 200%, by which dosage compensation is achieved. On the other hand, the increased gene dosage effects (150%) in metafemales are cancelled by the inverse dosage effects (67%) to equalize their expressions in normal females.