Among the progeny of a heterozygous round (Aa) × homozygous wrinkled (aa) testcross, three seeds are chosen at random. What is the probability that two seeds are round and the other is wrinkled?

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The cross Aa × aa yields two possible genotypes: Aa (round) and aa (wrinkled) in a 1:1 ratio. For three seeds, the probability of two being round (Aa) and one being wrinkled (aa) can be calculated using the binomial probability formula, which in this case is 3*(1/2)^3, because there are three ways to pick two round seeds and one wrinkled seed out of three (round-round-wrinkled, round-wrinkled-round, wrinkled-round-round), and each seed has a 1/2 chance of being round or wrinkled.

Among the Progeny of a Heterozygous Round (Aa) × Homozygous