In complementary genes, the dihybrid ratio of 9:3:3:1 is modified to

Options

A. 9:7
B. `12:3:1`
C. `15:1`
D. `13:3`

Answer

To solve the question regarding the modification of the dihybrid ratio in complementary genes, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Dihybrid Ratio**:
The typical dihybrid ratio for two independently assorting genes is 9:3:3:1. This ratio arises when both genes are dominant and do not interact with each other.

**Hint**: Recall the basic Mendelian genetics and the typical dihybrid cross results.

2. **Define Complementary Genes**:
Complementary genes are non-allelic genes that work together to produce a specific phenotype. In this case, both genes need to be dominant to express a particular trait.

**Hint**: Think about how two different genes can influence the same trait when both are present in their dominant forms.

3. **Analyze the Phenotypic Ratio**:
In the case of complementary genes, the presence of at least one dominant allele from each gene is required to express the dominant phenotype. If either gene is in the recessive form, the recessive phenotype will be expressed.

**Hint**: Consider how the presence of dominant and recessive alleles affects the overall phenotype.

4. **Calculate the Modified Ratio**:
When both genes are complementary, the phenotypic ratio changes from 9:3:3:1 to 9:7. This means that out of the total offspring, 9 will show the dominant phenotype (e.g., purple color) and 7 will show the recessive phenotype (e.g., white color).

**Hint**: Remember that the total number of phenotypes must still add up to the total number of offspring, but the distribution changes due to the interaction of the genes.

5. **Conclusion**:
Therefore, in complementary genes, the dihybrid ratio of 9:3:3:1 is modified to 9:7.

**Hint**: Summarize the findings to confirm the modified ratio.

### Final Answer:
In complementary genes, the dihybrid ratio of 9:3:3:1 is modified to **9:7**.