Two parents are phenotypically normal, but one of their four biological children has a typical autosomal recessive trait. The other three children are phenotypically normal. It is very likely that:
A) the affected child is a girl.
B) the affected child is a boy.
C) the trait was expressed by one of the grandparents of the children.
D) the parents are both heterozygous for the trait.
E) if the affected child eventually marries a phenotypically normal spouse, all of their children will have the trait.

Question

Quizplus · Accepted Answer

For an autosomal recessive trait to be expressed, both parents must be carriers (heterozygous) for the trait, meaning they each have one recessive allele.

Two Parents Are Phenotypically Normal, but One of Their Four