Question

In some flowers, a purple pigment is synthesized from a red precursor pigment. In the absence of all pigment, flowers are white. A pure-breeding plant with red flowers was crossed to a pure-breeding plant with white flowers. All of the F 1 plants had white flowers. The F 1 plants were crossed to each other, and the F 2 consisted of 165 plants: 123 with white flowers, 32 with purple flowers, and 11 with red flowers. How do these results suggest that flower color is determined

Answer 1

The results of the cross suggest a two-step genetic process for flower color inheritance involving epistasis, where the expression of one gene masks the expression of another gene, leading to a deviation from the classic 9:3:3:1 dihybrid cross ratio.

Step-by-step explanation:

The student's question regards the inheritance patterns of flower color in plants, which is a classic topic in Mendelian genetics. In the cross between a pure-breeding red-flowered plant and a pure-breeding white-flowered plant, all the F1 offspring had white flowers, indicating that white is the dominant phenotype. When these F1 plants were crossed with each other to produce F2 offspring, the results showed a non-standard ratio of white to purple and red flowers. This suggests a two-step genetic process where the purple pigment is synthesized from a red precursor, and the presence of white flowers indicates the absence of all pigment. Given the numbers from the F2 generation (123 white, 32 purple, and 11 red), this does not exactly follow the expected 9:3:3:1 dihybrid ratio but indicates a form of interaction between two different genes, possibly a form of epistasis, where one gene can mask the expression of another gene.

Answer 2

Answer: Recessive epistasis

Explanation:

Epistasis is a gene interaction it influences a phenotype. Genes can mask each other effect with one been dominant over the other or they can both be expressed to produce a new trait.

It is the conditional relationship between two genes that can determine a single traits. When there are two alleles that dictate phenotypes they can affect one another such that allele of one gene is recessive to one that is a dominant allele over the other.

A recessive epistasis occur when a recessive allele mask the expression of both recessive and dominant allele of another locus. Allele for white color mask the effect of other alleles expressing itself over them to give a phenotypic ratio of 9:3:4 a deviation from normal mendelian principle.

When a dominant allele masks the effect of both dominant and recessive alleles at another locus, it is a dominant epistasis.