A baby girl is born with hemophilia, which is an X-linked recessive disorder. What are the most likely genotypes of her parents?
- A. The mother is a carrier and the father is normal
- B. The mother is hemophiliac and the father is normal
- C. The mother is carrier and the father is hemophiliac
- D. Both are normal
Explanation
A girl has two X chromosomes and needs the recessive allele on both, one from each parent, so the father must be haemophiliac himself and the mother must carry at least one copy. A carrier mother with a normal father could only produce affected sons, which is why the first option fails. This is why affected females are so rare.
Related questions
Red green colour blindness is far commoner in men than in women because
A woman who is a carrier for colour blindness marries a man with normal colour vision. The probability that any son of theirs is colour blind is
Haemophilia A is caused by the deficiency of
A colour blind girl can be born only if
The sex of a human child is determined by