A student is investigating patterns of inheritance by crossing two pea plants. She creates the Punnett square shown below. Which explanation of the inheritance of shape in pea plants is supported by the Punnett square? A. The alleles for shape show a pattern of codominance. B. The alleles for shape show a pattern of incomplete dominance. C. The allele for round shape (R) is dominant to the allele for wrinkled shape (r). D. The allele for wrinkled shape (r) is dominant to the allele for round shape (R).

Answer 1

To determine which explanation of the inheritance of shape in pea plants is supported by the Punnett square, we need to assess the typical inheritance patterns of traits in pea plants, specifically the trait for shape, which includes round (R) and wrinkled (r) seeds.

In pea plants:

• The allele for round seeds (R) is known to be dominant over the allele for wrinkled seeds (r).
• This means that when a plant has at least one dominant allele (R), the seeds will exhibit the round shape.

If the Punnett square shows combinations of R and r alleles resulting in round seeds in the offspring (e.g., Rr or RR), this supports option C, which states that "the allele for round shape (R) is dominant to the allele for wrinkled shape (r)."

On the other hand:

• Option A (codominance) would imply that both alleles express equally in the phenotype, which is not the case for these seed shapes.
• Option B (incomplete dominance) would suggest a blending of traits, which also does not occur with round versus wrinkled peas.
• Option D contradicts the established dominance of R over r.

Based on these analyses, the correct explanation supported by the Punnett square is C. The allele for round shape (R) is dominant to the allele for wrinkled shape (r).