In pea plants, round peas (R) are dominant to wrinkled peas (r). You do a test cross between a pea plant with wrinkled peas (genotype rr) and a plant of unknown genotype that has round peas. You end up with three plants, all which have round peas. From this data, can you tell if the parent plant is homozygous dominant or heterozygous?

Data in Figure 8.9

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YY Yellow Gametes F₁ Gametes Monohybrid Cross Yy Each homozygous Green parent in the P generation produces only one kind of gamete. Yellow Yellow Yy YY Yellow Green Yy yy Phenotypes Genotypes YY Yellow Yy Green yy The heterozygous F₁ offspring produces two kinds of gamete. Self-pollination of the F₁ offspring produces F₂ offspring with a 3:1 ratio of yellow to green seeds. Ratios Genotype Phenotype ratio ratio 3 1 1 2 1