Question

question 15
a man who is a carrier for pku marries a woman who does not have the disease. they have a son and find out that he has pku. what must be true in order for this to occur?
○ the woman is homozygous dominant
○ the woman is homozygous recessive
○ the woman is also a carrier for the disease
○ there is no way that this could happen so the hospital has made a mistake

Explanation:

PKU (Phenylketonuria) is an autosomal recessive disorder. Let the allele for normal be \( A \) and for PKU be \( a \). The man is a carrier, so his genotype is \( Aa \). For their son to have PKU (genotype \( aa \)), the son must inherit \( a \) from both parents. The man can pass \( a \), so the woman must also pass \( a \). If the woman does not have the disease, for her to pass \( a \), she must be a carrier (\( Aa \)) (since if she were homozygous dominant \( AA \), she can only pass \( A \); if homozygous recessive \( aa \), she would have the disease, which she doesn't). So the correct condition is the woman is also a carrier for the disease.

Answer:

the woman is also a carrier for the disease