Question

A particular flower can be purple, blue, red, or white. A pure-breeding purple plant is crossed with a pure-breeding white plant and the F 1 are then crossed to produce an F 2 generation. What might a 9:3:4 phenotype ratio in the F2 indicate?

- reciprocal recessive epistasis
- dominant epistasis
- additivity
- co-dominance
- recessive epistasis

Answer 1

A 9:3:4 phenotype ratio in the F2 generation indicates recessive epistasis, where the expression of one gene is masked by the expression of another.

Step-by-step explanation:

The question asks about a 9:3:4 phenotype ratio in the F2 generation from a cross between pure-breeding purple and white flowers. This ratio suggests a specific type of epistasis. In Mendel's experiments, he observed a 3:1 phenotypic ratio in many of his monohybrid crosses, which is indicative of a dominant and recessive allele pattern. However, the 9:3:4 ratio does not fit this simple pattern and is indicative of a more complex genetic interaction. The correct interpretation of a 9:3:4 ratio is recessive epistasis, where one gene locus masks or reduces the expression of a gene at a second locus.