Interaction of epistatic genes shows the ratio

Options

A. `9:6:1`
B. `13:3`
C. `12:3:1`
D. `15:1`

Answer

To solve the question regarding the interaction of epistatic genes and the resulting phenotypic ratio, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Epistasis**:
- Epistasis occurs when the effect of one gene (the epistatic gene) masks or modifies the effect of another gene (the hypostatic gene). This interaction can lead to different phenotypic ratios than those expected from simple Mendelian inheritance.

2. **Recall the Dihybrid Cross Ratio**:
- In a typical dihybrid cross involving two independently assorting genes, the expected phenotypic ratio is 9:3:3:1. This ratio represents the combinations of dominant and recessive traits from both genes.

3. **Identify Non-Additive Effects**:
- When the effects of genes are not additive, it indicates that the interaction between the genes is more complex. In such cases, the phenotypic ratio changes from the expected 9:3:3:1.

4. **Calculate the New Ratio**:
- For epistatic interactions, the phenotypic ratio can often be simplified. If we consider that two genes are involved and one gene masks the effect of another, we can derive the new ratio.
- The 9 (dominant for both traits) and 3 (dominant for one trait and recessive for the other) combine to give us 12, while the remaining 3 (recessive for one trait and dominant for the other) and 1 (recessive for both traits) remain as they are.
- Thus, the ratio becomes 12:3:1.

5. **Select the Correct Answer**:
- From the options provided, the ratio that matches our calculation is 12:3:1. Therefore, the correct answer is option C.

### Final Answer:
The interaction of epistatic genes shows the ratio of **12:3:1**.