Two carriers (Aa × Aa) of a recessive trait have two children. What is the probability that at least one child is aa?
Correct answer B. 7/16
Explanation
P(neither is aa) = (3/4)² = 9/16, so P(at least one aa) = 1 − 9/16 = 7/16. Calculating the complement is quicker than adding separate cases.
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