Dosage Compensation

Dosage compensation is the regulation of X-Chromosome expression to ensure equal phenotype expression in both males and females of a species. Equal expression is typically achieved by silencing one of the X Chromosomes in females. 
However, biological methods for dosage compensation can be regulated differently depending on the species. For example, male fruit flies double the expression of genes along the X chromosome instead of full inactivation of one of the female X chromosomes. 
Wikipedia & Dosage compensation in Drosophila, Stanford University.