Question

What is the dihybrid phenotypic ratio for recessive epistasis in an F22 generation?

(a) 9:3:3:1

(b) 9:6:1

(c) 9:3:4:1

(d) 9:3:4

I had been asked this question during a job interview.

The question is from Epistasis in chapter Extension and Deviation from Mendelian Genetic Principles of Cytogenetics

Answer 1

The correct answer is (d) 9:3:4

Explanation: In case of recessive epistasis the expression of A/- b/b and a/a b/b  are the same where B is the epistatic locus and A is the hypostatic locus. So the dihybrid ratio is modified to 9:3:4.