Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. They rarely live past their 20s. How likely is it for a woman to have this condition? O One-half of the daughters of an affected man would have this condition. O Very rarely: it is rare that an affected male would mate with a carrier female. Women can never have this condition. O One-fourth of the daughters of an affected father and a carrier mother could have this condition. Only if a woman is XXX could she have this condition.

Each daughter born to a woman that is positive for a dystrophin mutation on one of her two X chromosomes possess a 50 percent likelihood of possessing the mutation and also becoming a carrier. Carriers at times do not show the disease symptoms but may give birth to a child that has the mutation or the disease condition. DMD carriers do have a higher chance of cardiomyopathy.

A man with DMD cannot transfer the affected gene to his sons since he passes to his son a Y chromosome, not the X chromosome. But he will definately transfer it to his daughters, since each daughter possess her father’s only X chromosome resulting in the daughters being carriers.

Hence, One-half of the daughters of an affected father and a carrier mother could have this condition.