Which of the follwing depicts the mendel's dilhybird ratio

Options

A. `3:1`
B. `9:3:3:1`
C. `9:7`
D. `15:1`

Explanation

To solve the question regarding Mendel's dihybrid ratio, we need to follow these steps:

### Step-by-Step Solution:

1. **Understanding Dihybrid Cross**: A dihybrid cross involves two traits, each represented by two alleles. In Mendel's experiments, he used traits such as seed shape (round vs. wrinkled) and seed color (yellow vs. green). Round (R) and yellow (Y) are dominant traits, while wrinkled (r) and green (y) are recessive traits.

2. **Setting Up the Parental Generation**: The parental generation (P) consists of two plants: one homozygous for both dominant traits (RRYY) and the other homozygous for both recessive traits (rryy).

3. **Gamete Formation**: Each parent produces gametes. The dominant parent can produce gametes with alleles RY, while the recessive parent produces gametes with alleles ry.

4. **F1 Generation**: When these gametes combine during fertilization, all offspring in the F1 generation will be heterozygous for both traits (RrYy). The phenotype of all F1 offspring will be round and yellow since both dominant traits are expressed.

5. **Selfing the F1 Generation**: To find the F2 generation, we perform a self-cross of the F1 plants (RrYy x RrYy).

6. **Gamete Formation in F1**: Each F1 plant can produce four types of gametes: RY, Ry, rY, and ry.

7. **Punnett Square**: We can set up a Punnett square with the gametes from both parents. This will help us visualize the combinations of alleles in the F2 generation.

8. **Phenotypic Ratio Calculation**: After filling out the Punnett square, we count the phenotypes:
- Round Yellow (RY): 9
- Round Green (rY): 3
- Wrinkled Yellow (Ry): 3
- Wrinkled Green (ry): 1

9. **Conclusion**: The phenotypic ratio for a dihybrid cross is 9:3:3:1. Therefore, the correct answer to the question is that Mendel's dihybrid ratio is 9:3:3:1.