Question

The ratio of phenotype in F${}_2$ generation of a dihybrid cross is___________

• A. 3 : 1
• B. 1 : 2 : 1
• C. 2 : 1
• D. 9 : 3 : 3 :1

Answer 1

The correct option is D 9 : 3 : 3 :1

For genes on separate chromosomes, each allele pair shows independent segregation. If the first filial generation (F${}_1$ generation) produces four identical offspring, the second filial generation, which occurs by crossing the members of the first filial generation, shows a phenotypic (appearance) ratio of 9 : 3 : 3 : 1.

For instance:

Round yellow x Wrinkled green

RRYY x rryy

RY ry

F${}_1$: RrYy (Round yellow)

Selfing of F${}_1$: RrYy x RrYy

Gametes: RY, Ry, rY, ry RY, Ry, rY, ry

From Punnett square: F${}_2$ gives a phenotypic ratio of 9 : 3 : 3 : 1