In Mendel's dihybrid cross with round-yellow and wrinkled-green seeds, what is the phenotypic ratio of the F2 generation?

1. Cross round-yellow (RRYY) with wrinkled-green (rryy); F1 is all RrYy round-yellow. 2. Self the F1 RrYy x RrYy; each parent makes four gamete types RY, Ry, rY, ry. 3. The 4x4 Punnett square gives 9 round-yellow, 3 round-green, 3 wrinkled-yellow, 1 wrinkled-green. 4. So the dihybrid phenotypic ratio is 9 : 3 : 3 : 1, option A. _Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 18 Genetics "Dihybrid Cross", p.271_