Recessive, X-linked: A gene on the X chromosome that expresses itself only when there is no different gene present at that locus (spot on the chromosome). For example, Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder. A DMD boy has the DMD gene on his sole X chromosome (and so is said to be hemizygous for DMD). Some girls who are heterozygotes for DMD can have DMD features in older age .
Reviewed on 9/7/2018