Question

A phenotypically normal woman marries a man with Wilson disease, a autosomal recessive disorder. They have a son who has Wilson disease. If you need two copies of the recessive allele to be affected and the mother doesn't have the disease, how did the son get it?
A. The woman had two recessive alleles.
B. The woman must have been a carrier of one recessive allele and one normal allele
C. The woman had two dominant alleles.
D. The man had two dominant alleles
E. The man had one dominant and one recessive allele.

Answer 1

Answer:

E. The man had one dominant and one recessive allele.

Explanation:

Woman marries a man with Wilson disease, a autosomal recessive disorder. The woman doesn't have the disease, the son got it. Therefore, the man has another dominant allele.