A man who is a dwarf due to achondroplasia and has normal vision marries a color-blind woman of normal height.The man's father was 6 feet tall,and both the woman's parents were of average height.Achondroplasia is autosomal dominant,and red-green color blindness is X-linked recessive.
What proportion of their sons would be color-blind and of normal height?
A)none
B)half
C)one out of four
D)three out of four

Question

Quizplus · Accepted Answer

Since achondroplasia is autosomal dominant, the man must have one allele for achondroplasia and one normal allele. Given that he is a dwarf, his children have a 50% chance of inheriting the allele for achondroplasia. For a son to be of normal height, he must inherit the normal allele, which happens 50% of the time. Red-green color blindness is X-linked recessive, and since the mother is color-blind, she can only pass on the allele for color blindness to her sons. Therefore, all sons will be color-blind. Combining these probabilities, 50% of their sons will be color-blind and of normal height.

A Man Who Is a Dwarf Due to Achondroplasia and Has