Question

On crossing red and white flowered plants the ratio of red and white flowered plants in F${}_2$ generation was 60 : 20, then on selfing the heterozygous red flowered plants, the offsprings would be

• A. 72 : 24
• B. 40 : 60
• C. 52 : 48
• D. 84 : 16

Answer 1

The correct option is A 72 : 24

Since the F${}_2$ generation ratio of red and white colour flower is 60:20 (3:1), the allele for red flower is completely dominant over that of white colour flower. If the red flower allele is denoted by R and that of white colour is denoted by r, the genotype of heterozygous red flowered plant will be Rr. This heterozygous red flowered plant will produce two types of gametes R and r. Selfing of heterozygous red flowered plants produce red and white colour flowers in 3:1 ratio. Option A (72:24) also show the same ratio. Hence, the correct option is A.

Gametes : Rr ---> Rr	R	r
R	RR red	Rr red
r	Rr red	rr white