Assertion:Ratio of complementary genes is 9:7.
Reason.Ratio of supplementary genes is `9:3:4`

Options

A. If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion .
B. If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion
C. If Assertion is true but the Reason is false.
D. If both Assertion and Reason are false.

Answer

To solve the question regarding the assertion and reason about complementary and supplementary genes, we can break it down step by step.

### Step-by-Step Solution:

1. **Understanding Complementary Genes:**
- Complementary genes are two different genes that work together to produce a single trait. When both genes are present, they complement each other's effects, and if either gene is absent, the trait is not expressed.
- The typical phenotypic ratio for complementary gene interactions in a dihybrid cross is 9:7. This means that out of 16 offspring, 9 will show the dominant phenotype, while 7 will show the recessive phenotype.

2. **Understanding the Assertion:**
- The assertion states that the ratio of complementary genes is 9:7. Based on the definition and understanding of complementary genes, this assertion is indeed correct.

3. **Understanding Supplementary Genes:**
- Supplementary genes are genes that can modify the expression of another gene. In this case, one gene can mask the effect of another, leading to a different phenotypic ratio.
- The typical phenotypic ratio for supplementary gene interactions is 9:3:4. This means that out of 16 offspring, 9 will show one phenotype, 3 will show another, and 4 will show a third phenotype.

4. **Understanding the Reason:**
- The reason states that the ratio of supplementary genes is 9:3:4. This is also correct based on the definition and understanding of supplementary genes.

5. **Conclusion:**
- Both the assertion and the reason are correct statements. However, the reason does not serve as a correct explanation for the assertion since they refer to different types of gene interactions (complementary vs supplementary).
- Therefore, the correct option is that both statements are true, but the reason is not the correct explanation for the assertion.

### Final Answer:
Both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.