MCAT Math Question 38: Answer and Explanation
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Question: 38
8. Assume that having blonde hair and blue eyes are independent recessive traits. If one parent is a carrier for each gene while the other parent is homozygous recessive for both genes, what is the probability that the first two offspring will both have blonde hair and blue eyes?
- A. 6.25%
- B. 25%
- C. 43.75%
- D. 50%
Correct Answer: A
Explanation:
Because one parent is homozygous for both traits, we are only concerned with the other parent. This parent has a 50% chance of transmitting each independent trait, and thus a 25% chance of transmitting both (0.5 × 0.5 = 0.25). This probability is the same for both pregnancies because they are independent events; thus, the probability that both children exhibit both traits is 0.25 × 0.25 = 0.0625, or 6.25%.