Definition: Refers to an inheritance pattern in which an individual has mutations in genes on the X chromosome. In males (who have only one X chromosome), one mutated copy of the gene in each cell is enough to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the condition. Because it is unlikely that females will have two mutated copies of this gene, males are affected by X-linked recessive disorders much more frequently than females. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons (no male-to=male transmission).