Question

On crossing red & white flowered plants the ratio of red and white flowered plants in $F_2$-generation was 60:20, then on setling 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

• Let the allele for red colour be represented by R and the allele for white colour by r.
• The possible genotype of plant is RR and rr. When RR is crossed with rr, the F1 phenotypic ratio will be all red (Rr). When F1 individuals are selfed i.e Rr x Rr, the F2 ratio will be 3:1 (60: 20).
• Now, when heterozygous (Rr) red flowered plant are crossed. Again the same cross i.e Rr x Rr, the ratio will be 3:1 (72: 24 among the given options). {because 72:24 = 3:1).
• So, (A) is the correct answer.