X-Linked Disease

Definition

The two sex chromosomes are X and Y. Males are characterized by an XY pair, and females are characterized by an XX pair. X-linked disease is a genetic disease caused by a mutation of a gene on the X-chromosome. Males will be affected, because they have only the one X-chromosome located mutant allele. Females show much less prevalence of disease, because to be affected they would need to receive a mutant allele from both parents.

For example, a disease such as Duchenne muscular dystrophy (DMD) is inherited, because the responsible mutated dystrophin gene is carried on the X chromosome. As males have only one X chromosome, the characteristics represented by its genes are typically expressed, whereas in females with two X chromosomes they are not. DMD is therefore considered an X-linked recessive genetic disease.

Duchenne Muscular Dystrophy