A modified dihybrid mendelian ratio of 9:3:4 shows

Options

A. supplementary genes
B. complementary genes
C. lethal genes
D. duplicate

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about a modified dihybrid Mendelian ratio of 9:3:4 and which genetic interaction this ratio corresponds to among supplementary, complementary, lethal, or duplicate genes.

2. **Identifying the Ratios**:
- In genetics, different interactions between genes produce specific phenotypic ratios:
- **Supplementary Genes**: 9:3:4
- **Complementary Genes**: 9:7
- **Lethal Genes**: 2:1
- **Duplicate Genes**: 15:1

3. **Analyzing Supplementary Genes**:
- Supplementary genes are those where two genes work together to produce a particular phenotype. An example is the seed coat color in certain plants, where the presence of dominant alleles from both genes leads to a unique phenotype.

4. **Example of Supplementary Genes**:
- In the case of seed coat color, let’s denote two genes as K and L:
- **K**: Produces khaki color
- **L**: Produces buff color
- The combinations of these alleles in the F1 generation (KkLl) can produce a third phenotype (chocolate) when both dominant alleles are present.

5. **Performing a Dihybrid Cross**:
- When you perform a dihybrid cross of these genes, the phenotypic ratio in the F2 generation will be:
- 9 (chocolate): 3 (khaki): 4 (buff)

6. **Conclusion**:
- Since the ratio of 9:3:4 corresponds to supplementary genes, the correct answer to the question is that this ratio occurs in supplementary genes.

### Final Answer:
The modified dihybrid Mendelian ratio of 9:3:4 occurs in **supplementary genes**.

---