Question

In a dihybrid cross between a true breeding round yellow seeded and true breeding wrinkled green seeded pea plant, the ratio of segregation of round and wrinkled seed traits in F2 is:

• A. 9:1
• B. 3:1
• C. 9:3
• D. 3:3

Hint:

Mendelian principles explain predictable inheritance patterns in dihybrid crosses.

Answer 1

The Correct Option is B

In a dihybrid cross between true-breeding round yellow (RRYY) and wrinkled green (rryy) pea plants, the F₂ ratio for round:wrinkled seeds is 3:1.

(A) 9:1 - Incorrect: This doesn't represent any standard Mendelian ratio.

(B) 3:1 - Correct: When considering only seed shape (ignoring color), the monohybrid ratio reasserts itself (3 round : 1 wrinkled).

(C) 9:3 - Incorrect: This represents partial phenotypic ratio (round yellow + round green).

(D) 3:3 - Incorrect: This would suggest equal proportions, which isn't observed.

The correct answer is (B) 3:1, demonstrating Mendel's Law of Segregation for a single trait (round vs wrinkled) within a dihybrid cross.