Question

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 the their children will have the trait.

Answer 1

d. the parents are both heterozygous for the trait. The most likely scenario is that both parents are heterozygous carriers for the autosomal recessive trait. The gender of the affected child cannot be determined. The trait could have been expressed by one of the grandparents of the children.

Step-by-step explanation:

The most likely scenario in this case is that both parents are heterozygous for the autosomal recessive trait. When both parents are carriers of a recessive trait, there is a 25% chance for their child to have the trait. In this case, one out of the four biological children has the recessive trait, so the parents are most likely both carriers.

The gender of the affected child cannot be determined based on the given information. The affected child could be either a boy or a girl.

It is also important to note that the trait could have been expressed by one of the grandparents of the children. If both parents are carriers, it is possible for one or both of their parents to also be carriers of the trait, which could explain the occurrence of the trait in one of their children.