A man and woman are both of normal pigmentation, but both have one parent who is albino without melanin pigmentation). Albinism is an autosomal not sex- linked) recessive trait. What is the probability that their first child will be an albino?

Question

Quizplus · Accepted Answer

Both parents are carriers of the allele for albinism since they have one albino parent each but have normal pigmentation themselves. This means they are both heterozygous (Aa) for the trait.

When they have children, each parent will randomly pass on one of their two alleles for the trait. Thus, the possible combinations for their children are:

AA (not possible since neither parent has two copies of the albino allele) 
Aa (25% chance)
aA (25% chance)
aa (25% chance)

Only the last combination (aa) will result in an albino child. Therefore, the probability of their first child being albino is 1/4 or 25%.

The correct answer is D) 1/4.

A Man and Woman Are Both of Normal Pigmentation, but Both