Question

The color varieties of sunflower pollen are determined by two interacting loci: A_B_ gives orange pollen, aaB_ gives yellow, and _ _bb produces cream colored. Assume that two fully heterozygous plants are crossed. Give the phenotypes (with frequencies) of the offspring. What type of gene interaction would account for these results?

Answer 1

AaBb × AaBb

Gametes	AB	Ab	aB	ab
AB	AABB orange	AABb orange	AaBB orange	AaBb orange
Ab	AABb orange	AAbb cream	AaBb orange	Aabb cream
aB	AaBB orange	AaBb orange	aaBB yellow	aaBb yellow
ab	AaBb orange	Aabb cream	aaBb yellow	aabb cream

Phenotypic ratio - 9 (orange) : 4 (cream) : 3 (yellow)

This is an example of epistasis. Epistasis is non allelic interaction between present alleles present at different gene locus.

One of the alleles mask effect of other alleles. The former is said to be epistatic over the latter which is hypostatic.

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