i am having difficulty with understanding how to do this even though it states instructions. Still does not make much sense. We are working with Prunet squares. I just can't grasp the concept.

1. YyRr x YyRr
2. Yellow round, Yellow round
3. YYRR, YYRr, YyRR, Yyrr, yyrr, Yyrr, yyRr, YyRr, yyRR
4.
F1 genotypes: YYRR, YYRr, YyRR, Yyrr, yyrr, Yyrr, yyRr, YyRr, yyRR
F1 Phenotypes: yellow round, yellow wrinkled, green round, green wrinkled