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 the man and woman have one parent who is albino, which means they both must be carriers of the recessive albinism allele. Therefore, their genotypes must be Aa (where A represents the dominant allele for normal pigmentation, and a represents the recessive allele for albinism).

When these two individuals have a child, there are four possible combinations of their gametes:

- The man can contribute an A allele and the woman can contribute an A allele: the child will be AA (normal pigmentation). 
- The man can contribute an A allele and the woman can contribute an a allele: the child will be Aa (normal pigmentation, but a carrier of albinism). 
- The man can contribute an a allele and the woman can contribute an A allele: the child will be Aa (normal pigmentation, but a carrier of albinism). 
- The man can contribute an a allele and the woman can contribute an a allele: the child will be aa (albino).

Of these four possibilities, there is only one where the child will be an albino (aa genotype). Therefore, the probability is 1/4 or 0.25.

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