A 21-year-old woman who has two brothers with Duchenne muscular dystrophy asks whether carrier status testing is appropriate for her. What is the best response?

Question

Quizplus · Accepted Answer

The genetic mutation for Duchenne muscular dystrophy is on the X chromosome and is transmitted in an X-linked recessive manner. Although the spontaneous mutation rate for this disease is relatively high, the fact that she has two brothers with the disorder, rather than just one, strongly suggests this mutation was inherited, not spontaneous. Thus, her mother is a carrier of an X-linked recessive genetic mutation. This young woman's risk for having inherited the mutation on her maternally derived X chromosome is 50%, not 100%. If she were a carrier, she may or may not have any symptoms of the disorder depending on which X is inactivated in her skeletal muscle and cardiac muscle tissues. The absence of symptoms does not clearly rule out a carrier status for her.

A 21-Year-Old Woman Who Has Two Brothers with Duchenne Muscular