## MCAT Question A Day - 9/22/14 - Answer!

**Color-blindness is a sex-linked recessive trait. A woman who is a carrier for the trait has two boys with a color-blind man. What is the probability that both boys are color-blind?**

**A.**0%

**B.**25%

**C.**50%

**D.**100%

*B is correct. According to the Punnett square, each time they have a boy, there is a 50% chance that he will be color-blind. The chance that both boys are colorblind is the chance of this happening twice, or (0.5)*

^{2}.

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