A polygenic trait is controlled by 3 genes A, B and C. In a cross AaBbCc `xx` AaBbCc, the phenotypic ratio of the offsprings was observed as :
`1:6xx:20xx:6:1` what is the possibe value of x?

Options

A. 3
B. 9
C. 15
D. 25

Answer

C

Explanation

Polygenes show polygenic inheritance or quantitative inheritance. As genes are present o differet chromosomes they will segregate independently during meiosis.
Types of gamets=`2^(n)`
Number of individuals in `F_(2)=("Types of gametes")^(2)=(2^(n))^(2)`
n=number of heterozygous genes present `=(2^(3))^(2)=8^(2)=64`individuals
`1+6+2x+20+6+1=64`
`2x=64-34`
`x=(30)/(2)=15`