In humans, the allele for red-green color blindness is X-linked and recessive (Xʳ; the dominant allele is called Xᴿ). A man with normal color vision marries a color-blind woman who gives birth to a color-blind daughter. What can be inferred from this information?
A) The woman is XᴿXʳ.
B) The man must be a carrier for the color blindness allele.
C) The daughter must be heterozygous.
D) The man is probably NOT the father of the daughter.

Question

Quizplus · Accepted Answer

A color-blind daughter must inherit one Xʳ allele from each parent. Since the father has normal vision, he cannot pass on an Xʳ allele, suggesting he is not the biological father.

In Humans, the Allele for Red-Green Color Blindness Is X-Linked