2002 AIPMT Principles of Inheritance and VariationMonohybrid Cross Easy Question 180 of 198 in Principles of Inheritance and Variation

A plant of $F_1$-generation with genotype \"AABbCC\"". On selfing of this plant what is the phenotypic ratio in $F_2$-generation : -"

A 3 : 1
B 1 : 1
C 9 : 3 : 3 : 1
D 27 : 9 : 9 : 9 : 3 : 3 : 3 : 1

The answer is A.

Solution

In the genotype AABbCC, only the gene pair B/b is heterozygous; AA and CC are homozygous.
On selfing, AA $\times$ AA gives all AA and CC $\times$ CC gives all CC, so these genes do not produce any variation in phenotype.
Bb $\times$ Bb gives BB : Bb : bb = 1 : 2 : 1, i.e. 3 dominant : 1 recessive in phenotype.
So the cross behaves like a monohybrid cross, and the phenotypic ratio in $F_2$ is 3 : 1.

Concept Only heterozygous gene segregates

Principles of Inheritance and Variation in past papers

198 questions from this chapter have appeared across 27 exam years.