To determine the expected ratio of yellow seeds to green seeds in the offspring of a cross between a heterozygous plant (Yy) and a homozygous recessive plant (yy), we can use a Punnett square to visualize the possible genotypes of the offspring.
1. Define the Genotypes of the Parents:
- Parent 1: Yy (heterozygous for yellow seeds)
- Parent 2: yy (homozygous recessive for green seeds)
2. Set up the Punnett Square:
The Punnett square helps us determine all possible combinations of the alleles from the parents.
| | y | y |
|---|---|---|
| Y | Yy| Yy|
| y | yy| yy|
Each cell in the table represents a possible genotype for the offspring.
3. Determine the Genotype of the Offspring:
From the Punnett square, we can see the genotypes of the offspring:
- Yy (yellow seeds)
- yy (green seeds)
- The genotypic combinations occur in these quantities:
- 2 Yy (yellow) offspring
- 2 yy (green) offspring
4. Determine the Phenotype Ratios:
- Yellow seeds (Yy): 2 offspring
- Green seeds (yy): 2 offspring
Therefore, the ratio of yellow seeds to green seeds is \(2:2\).
5. Simplify the Ratio:
- The ratio \(2:2\) can be simplified to \(1:1\).
Thus, the expected ratio of yellow seeds to green seeds in the offspring is \(2:2\).
Hence, the correct answer is:
A. [tex]\(2:2\)[/tex]
