Epigenetic aspects of X-chromosome dosage compensation

The X chromosomes of mammals and fruit flies exhibit unusual properties tha t have evolved to deal with the different dosages of X-linked genes in mate s (XY) and females (XX). The X chromosome dosage-compensation mechanisms di scovered in these species are evolutionarily unrelated, but exhibit surpris ing parallels in their regulatory strategies. These features include the im portance of noncoding RNAs, and epigenetic spreading of chromatin-modifying activities.