Duchenne muscular dystrophy (DMD)is caused by 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?
A) Women can never have this condition.
B) One-half of the daughters of an affected man could have this condition.
C) One-fourth of the children of an affected father and a carrier mother could have this condition.
D) Very rarely would a woman have this condition; the condition would be due to a chromosome error.
E) Only if a woman is XXX could she have this condition.

Question

Duchenne muscular dystrophy (DMD)is caused by 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?
A) Women can never have this condition.
B) One-half of the daughters of an affected man could have this condition.
C) One-fourth of the children of an affected father and a carrier mother could have this condition.
D) Very rarely would a woman have this condition; the condition would be due to a chromosome error.
E) Only if a woman is XXX could she have this condition.

Quizplus · Accepted Answer

Duchenne muscular dystrophy is an X-linked recessive disorder, which means that the gene mutation is carried on the X chromosome. Since women have two X chromosomes, they would need two copies of the mutation (one on each X chromosome) to express the disease. This is rare because the chances of both X chromosomes having the same mutation are low. Women can still be carriers of the disease if they have one copy of the mutation on one X chromosome and a normal gene on the other X chromosome. However, they are not affected by the disease. If a woman were to have the disease, it would likely be due to a chromosome error.

Duchenne Muscular Dystrophy (DMD)is Caused by a Gene on the Human