X-Linked Recessive

Refers to an inheritance pattern where the gene causing a disorder or trait is located on the X chromosome. Most males have one X chromosome and one Y chromosome (XY). Since most males have only one X chromosome, a gene change in their one and only copy of the X chromosome is enough to cause the disorder or trait. Females can have X-linked disorders, but this is not common. Most females have two copies of the X chromosome (XX) and therefore they are more likely to have at least one normal copy of the gene and not be affected. See recessive.