Question

Albinism is a recessive trait. A man and woman are both of normal pigmentation, but both have one parent who is albino (without melanin pigmentation). What is the probability that their first child will be an albino

Answer 1

The man and woman both have albino parents (aa) so one of their alleles will be for the albino trait (a). But since they both have normal pigmentation, their other allele must be for the dominant pigmented trait (A), making their genotypes heterozygous (Aa). If you make a quick punnet square with each of their genotypes on a side, there is a 1/4 or 25% chance that the combination of their alleles will result in an albino (aa) child.

Answer 2

use the generation tree starting by the grandparents as first generation and the parents as second generation until the child as third generation