Question

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Duchenne muscular dystrophy is a sex-linked disorder. If a father has a normal X chromosome and the mother is a carrier, what are the odds that a male child would have Duchenne muscular dystrophy? what are the odds for a female child to have the disease or be a carrier?

Answer 1

Sex-linked diseases are passed down through families through one of the X or Y chromosomes. X and Y are sex chromosomes.

Dominant inheritance occurs when an abnormal gene from one parent causes disease even though the matching gene from the other parent is normal. The abnormal gene dominates.

Recessive inheritance is when both matching genes must be abnormal to cause disease. If only one gene in the pair is abnormal, the disease does not occur, or is mild. Someone who has one abnormal gene (but no symptoms) is called a carrier. A carrier can pass this abnormal gene to his or her children.

The term "sex-linked recessive" usually refers to X-linked recessive.