A man who is a dwarf with achondroplasia and normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their daughters might be expected to be color-blind with achondroplasia?
A) none
B) half
C) one out of four
D) three out of four

Question

Quizplus · Accepted Answer

Since the man has normal vision, he does not carry the allele for color blindness. The woman is color-blind, meaning she has two X chromosomes with the color-blind allele. Their daughters will inherit one X chromosome from each parent, so they will all be carriers for color blindness but not color-blind themselves. For achondroplasia, the man is a dwarf, so he has one dominant allele for achondroplasia. Each daughter has a 50% chance of inheriting the achondroplasia allele. Therefore, none of the daughters will be color-blind with achondroplasia.

A Man Who Is a Dwarf with Achondroplasia and Normal