In a dihybrid cross, `F_(2)` phenotypic ratio is 13:3. It is case of

Options

A. Complementary genes
B. Epistatic genes
C. Multigentic inheritance
D. Incomplete dominance

Answer

To solve the question regarding the dihybrid cross with an F2 phenotypic ratio of 13:3, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Dihybrid Cross**: A dihybrid cross involves two traits, each controlled by different genes. In a typical Mendelian dihybrid cross, the F2 generation exhibits a phenotypic ratio of 9:3:3:1.

2. **Identify the Given Ratio**: The question states that the F2 phenotypic ratio is 13:3. This indicates a deviation from the typical Mendelian ratio, suggesting a different genetic interaction.

3. **Recognize the Type of Genetic Interaction**: The ratio of 13:3 is indicative of epistasis, where one gene masks or modifies the expression of another gene. In this case, the presence of one allele can suppress the expression of another allele, leading to the observed ratio.

4. **Confirm the Concept of Epistasis**: In epistasis, the gene that masks the effect of another gene is referred to as the epistatic gene. This interaction can lead to modified Mendelian ratios, such as 13:3, which is a result of the interaction between dominant and recessive alleles.

5. **Eliminate Other Options**:
- **Complementary Genes**: Would typically yield a 9:7 ratio.
- **Multigenic Inheritance**: Would not yield a simple ratio like 13:3; it usually results in a continuous variation.
- **Incomplete Dominance**: Would produce a different phenotype ratio, not 13:3.

6. **Conclude the Correct Answer**: Based on the analysis, the correct answer to the question is that the F2 phenotypic ratio of 13:3 is a case of **epistatic genes**.

### Final Answer:
The correct option is **epistatic genes**.

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