Dosage compensation mechanisms in human ( Homo sapiens ), fly ( Drosophila melanogaster ), and worm ( C. elegans ). X chromosome dosage needs to be equalized between the sexes and relative to the autosomes. In humans, females with two X chromosomes undergo X inactivation of one chromosome; the remaining active X up-regulates its genes twofold. In flies, both female X chromosomes are active; male X-linked genes are up-regulated twofold. In worms, which utilize a hermaphrodite/male sex determination pathway, hermaphrodites express X-linked genes at half the rate of males, with both genotypes expressing two times the amount of X-linked genes[39, 53]. Chromosomes are not drawn to scale.