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:
Show Hint
Mendelian principles explain predictable inheritance patterns in dihybrid crosses.
- 9:1
- 3:1
- 9:3
- 3:3
The Correct Option is B
Approach Solution - 1
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.
Approach Solution -2
In a dihybrid cross, two traits are considered. For pea plants, the round (R) and wrinkled (r) seed shape and yellow (Y) and green (y) seed color are studied. A cross between round yellow-seeded (RRYY) and wrinkled green-seeded (rryy) plants produces F1 hybrids (RrYy), all with round yellow seeds. In the F2 generation, the segregation of the seed shape traits (round and wrinkled) follows a 3:1 ratio (dominant to recessive) because of Mendelian inheritance.
Option (B) is correct because the ratio of round to wrinkled seeds in F2 generation is 3:1.
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