Question

A true-breeding blue rose is crossed to a true-breeding white rose. TheF1 generation are all pink. The F1 roses are crossed and the resulting plants are as follows: 251 blue, 55 pink and 9 white. What inheritance pattern do you see for rose color?

- Dominant Epistasis
- Additive Gene Interaction
- Reciprocal Recessive Epistasis
- Incomplete Dominance

Answer 1

The inheritance pattern observed in the cross of true-breeding blue and white roses, resulting in all pink F1 offspring and a 1:2:1 ratio of blue, pink, and white F2 offspring, is an example of incomplete dominance.

Step-by-step explanation:

Inheritance Pattern in Rose Color

The inheritance pattern displayed by the cross of true-breeding blue and white roses leading to an F1 generation with all pink roses, and a subsequent generation with blue, pink, and white roses follow the pattern of incomplete dominance. Unlike the Mendelian dominant and recessive allele interactions that Gregor Mendel observed in pea plants, incomplete dominance results in an intermediate phenotype in the heterozygote. This phenomenon explains why the first-generation (F1) hybrids were all pink—a blend between blue and white.

When the F1 hybrids were crossed, the results were not in the Mendelian ratio of 3:1. Instead, they showed a ratio close to 1:2:1 for blue:pink:white, which is consistent with incomplete dominance. In this pattern, neither allele is completely dominant over the other, and the heterozygote has a distinct phenotype that is a mixture of the phenotypes of both homozygotes.

In this case, the blue allele (B) and the white allele (W) combine to produce the pink phenotype (BW). The F2 generation ratio of blue (BB), pink (BW), and white (WW) roses can be used to confirm this pattern of inheritance.