Question

In F2 progeny of dihybrid cross in pea plant the ratio of genotypes YyRR, yyRR, YyRR, Yyrr is

• A. 2:3:3:2
• B. 1:1:2:2
• C. 4:1:2:1
• D. 3:1:1:2

Hint:

In a dihybrid cross, the genotype ratio often follows 1:1:2:2 for traits where one gene shows a dominant-recessive pattern and the other exhibits independent assortment.

Answer 1

The Correct Option is B

Genotypic Ratios in a Dihybrid Cross

In a dihybrid cross involving two traits, the genotype combinations in the F₂ progeny will follow the ratios based on Mendelian genetics:

• YyRR: This genotype arises from the cross of Yy and RR parents.
  The ratio of this genotype is 1.
• yyRR: This genotype arises from the cross of yy and RR parents.
  The ratio of this genotype is 1.
• YyRR: The cross will give this genotype with a ratio of 2.
• Yyrr: This genotype arises from the cross of Yy and rr parents.
  The ratio of this genotype is 2.

Thus, the correct ratio of genotypes is 1:1:2:2.

Therefore, the correct answer is (2) 1:1:2:2.