Question

Which of the following ratios indicates an epistatic interaction

( select all that apply!)
A. 3:1
B. 9:7
C. 9:3:4
D. 9:3:3:1

Answer 1

C. 9:3:4

Step-by-step explanation:

F2 9:3:4 phenotypic ratio demonstrates recessive epistatic interaction. Here, recessive allele of one gene masks the effect of another gene. Suppose the two genes are A and B. Let their recessive counterparts be a and b. If "a" masks the effect of both B and b, it means that the two genes are showing recessive epistatic relationship. So the phenotype ratio would change from 9:3:3:1 to :

A_B_ = phenotype 1 = 9

A_bb = phenotype 2 = 3

aaB_ = phenotype 3 = 3

aabb = phenotype 3 = 1

Hence, the final ratio would be 9:3:4. Coat colour of labrador shows 9:3:4 ratio.