Mendelian principles explain predictable inheritance patterns in dihybrid crosses.
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.
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.
Match the following:
List I | Name | List II | Contribution |
---|---|---|---|
A | Hugo de Vries | I | Mutations |
B | Sturtevant | II | Gene Mapping |
C | Morgan | III | Linkage |
D | Sutton and Boveri | IV | Chromosomal theory |