A plant that has round and yellow seeds (RrYy) is crossed with a plant that has round and yellow seeds (RrYy). What is the ratio of the offspring that will have round and yellow seeds? Key: R is equal to round r is equal to wrinkled Y is equal to yellow y is equal to green

For each trait in an RrYy × RrYy cross, the dominant phenotype appears in 3 out of 4 offspring: 3/4 are round and 3/4 are yellow. Because the traits assort independently, multiply the probabilities: 3/4 × 3/4 = 9/16. Thus, 9 out of 16 offspring are expected to have round and yellow seeds, choice D.

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