Albinism is inherited as a recessive trait. An albino woman is married to a man with normal coloring and their first child is an albino. What was the genotype of the man?
A) homozygous dominant
B) heterozygous
C) homozygous recessive
D) incompletely dominant
E) sex-linked recessive

Question

Quizplus · Accepted Answer

Since albinism is a recessive trait, it is possible for the albino woman to be homozygous recessive (aa) and the man to be heterozygous (Aa) for normal coloration. The Punnett square for a cross between an aa and Aa individual shows that there is a 50% chance of their child being albino (aa) and a 50% chance of their child having normal coloring (Aa). The fact that their first child is albino confirms that the man must be carrying one copy of the albino allele. Therefore, his genotype is heterozygous (Aa).

Albinism Is Inherited as a Recessive Trait