In melons, spots (S) are dominant to no spots (s) and bitterness (B) is dominant to sweet (b). Answer the following questions that arise from a crossing of a homozygous dominant plant with a homozygous recessive plant. Assume Mendelian inheritance. I. What is the F2 phenotypic ratio if the F1 generation is intercrossed?

• A. 12:3:1
• B. 4:3:2:1
• C. 9:3:3:1
• D. 3:1

Answer: (C)

Verified step by step guidance

1. Identify the genotypes of the parent plants. The homozygous dominant plant has the genotype SSBB, and the homozygous recessive plant has the genotype ssbb.
2. Determine the genotype of the F1 generation. Since the F1 generation results from crossing SSBB with ssbb, all F1 offspring will have the genotype SsBb.
3. Understand that the F1 generation is heterozygous for both traits (spots and bitterness), meaning they have the potential to produce a variety of combinations in the F2 generation.
4. Perform a dihybrid cross using the F1 generation (SsBb x SsBb). Set up a Punnett square to determine the possible genotypes of the F2 generation.
5. Calculate the phenotypic ratio from the Punnett square results. The typical phenotypic ratio for a dihybrid cross involving two traits with complete dominance is 9:3:3:1, representing the combinations of dominant and recessive traits.