Question

How many different phenotypes and genotypes are obtained in Mendel’s ${\text{F}}_2$ generation of dihybrid cross?

A) 4 phenotypes and 9 genotypes
B) 4 phenotypes and 16 genotypes
C) 16 phenotypes and 8 genotypes
D) 2 phenotypes and 16 genotypes

Answer 1

The correct answer is (A).

In Mendel's dihybrid cross, two traits were considered. For a dihybrid cross for seed colour and seed type, he crossed two homozygous varieties, round yellow seeded plants (RRYY) with wrinkled green seeded plants (rryy).
It was followed by the selfing of ${\text{F}}_1$ progeny which were round yellow seeded (RrYy).
The Punnett square here shows the different combinations of ${\text{F}}_2$ progeny obtained.

The ${\text{F}}_2$ progeny of Mendel’s dihybrid cross exhibit four different phenotypes: round yellow, round green, wrinkled yellow and wrinkled green.

There are 9 different genotypes:

• RRYY, RRYy, RrYY, RrYy - 4 genotypes of the round yellow phenotype
• RRyy, Rryy- 2 genotypes of the round green phenotype
• rrYY, rrYy- 2 genotypes of the wrinkled yellow phenotype
• rryy- 1 genotype of the wrinkled green phenotype