Ratio of complementary genes is

Options

A. `9:3:4`
B. `12:3:1`
C. `9:3:3:4`
D. `9:7`

Answer

To determine the ratio of complementary genes, we can follow these steps:

### Step 1: Understand Complementary Genes
Complementary genes are two different genes that work together to produce a particular phenotype. When both genes are present in the dominant form, they produce a specific trait. If one gene is recessive, the dominant trait may not be expressed.

### Step 2: Identify the Ratios
We need to analyze the provided options to determine which one corresponds to complementary gene interaction. The options given are:
1. 9:3:4
2. 12:3:1
3. 9:3:3:1
4. 9:7

### Step 3: Analyze Each Option
- **Option 1 (9:3:4)**: This ratio indicates a recessive epistasis, not complementary genes.
- **Option 2 (12:3:1)**: This ratio indicates dominant epistasis, not complementary genes.
- **Option 3 (9:3:3:1)**: This ratio is the typical dihybrid cross ratio and does not represent complementary gene interaction.
- **Option 4 (9:7)**: This ratio indicates complementary gene interaction, where both genes need to be dominant to express the phenotype.

### Step 4: Conclusion
The correct answer for the ratio of complementary genes is **9:7**.