Question

Duchenne muscular dystrophy is a recessive X-linked allele. A woman heterozygous for Duchenne marries a man who is normal. What percentage of the females would be heterozygous carriers of Duchenne?

Answer 1

Step-by-step explanation:

If a woman is heterozygous for Duchenne muscular dystrophy (DMD), it means that she has one normal X chromosome and one X chromosome with the DMD mutation. Since DMD is a recessive X-linked allele, the normal X chromosome will mask the effects of the DMD mutation.

When this woman has children, each child has a 50% chance of inheriting the normal X chromosome and a 50% chance of inheriting the X chromosome with the DMD mutation. Therefore, the possible outcomes for her children are:

50% chance of inheriting the normal X chromosome from the mother and a normal X chromosome from the father (XX), resulting in a normal female offspring

50% chance of inheriting the X chromosome with the DMD mutation from the mother and a normal X chromosome from the father (XDX), resulting in a female carrier of DMD.

Therefore, the percentage of females who would be heterozygous carriers of Duchenne when a woman heterozygous for DMD marries a normal man is 50%.