To solve this problem regarding Mendel's expected ratio for a dihybrid cross, we need to understand Mendel's experiments and the pattern they revealed.
Gregor Mendel, through his experiments with pea plants, determined the rules of heredity. One of his key experiments considered a dihybrid cross, which involves two traits. A classic example includes examining traits such as seed shape (round or wrinkled) and seed color (yellow or green).
For a dihybrid cross, Mendel crossed plants that were heterozygous for both traits. The parents in this case are both RrYy, where:
- R = dominant allele for round seeds
- r = recessive allele for wrinkled seeds
- Y = dominant allele for yellow seeds
- y = recessive allele for green seeds
The expected ratio of the phenotypes in the progeny (offspring) can be determined by the combination of these alleles. According to Mendel's findings, the expected phenotypic ratio for a dihybrid cross in the F2 generation is:
- 9 exhibiting both dominant traits (Round Yellow)
- 3 exhibiting the dominant trait for the first characteristic and the recessive for the second (Round Green)
- 3 exhibiting the recessive trait for the first characteristic and the dominant for the second (Wrinkled Yellow)
- 1 exhibiting both recessive traits (Wrinkled Green)
Thus, the expected ratio is 9:3:3:1.
Given the options:
1. 4:1:1:10
2. 9:3:3:1
3. 9:4:2:1
4. 6:2:2:6
The expected ratio according to Mendel's experiments for a dihybrid cross is clearly:
9:3:3:1
Therefore, the correct answer is the second option, 9:3:3:1.
