Question

A polygenic trait is controlled by 3 genes A,B and CIn a cross AaBbCc x AaBbCc,the phenotypic ratio of the offsprings was observed as 1:6::20:x:6:1 What is the possible value of x? (1)3 (2)9 (3)15 (4)25

Answer 1

Answer:

In polygenic inheritance, a particular trait is controlled by 3 different genes. The given problem is of polygenic inheritance. In this, phenotypic ratio is 1:6:15:20:15:6:1 instead of 27:9:9:9:3:3:3:1 in F2 generation. In the given example, the genotype of parents is AaBbCc and AaBbCc. They will produce gametes ABC, ABc, Abc, abc, aBC, aBc, abC, AbC. The phenotypic ratio will be 1:6:15:20:`15:6:1.

Thus, the correct answer is (3).'15.'

Answer 2

Answer:

A polygenic trait is controlled by 3 genes A,B and CIn a cross AaBbCc x AaBbCc,the phenotypic ratio of the offsprings was observed as 1:6::20:x:6:1 What is the possible value of x? (1)3

(2)9

(3)15 ✔✔

(4)25