Failure of one gene to express it in the presence of a non-allelic gene is known as

Options

A. codominance
B. hypostasis
C. incomplete dominance
D. epistasis

Answer

To solve the question "Failure of one gene to express in the presence of a non-allelic gene is known as," we will follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about a specific genetic phenomenon where one gene's expression is inhibited or masked by another gene that is not allelic (not an alternative form of the same gene).

2. **Identifying Key Terms**:
- **Non-allelic gene**: This refers to a gene that is located at a different locus on a chromosome and does not compete with the first gene for expression.
- **Expression**: This refers to the manifestation of a gene's effect in the phenotype.

3. **Exploring Genetic Concepts**:
- **Co-dominance**: This occurs when two alleles are expressed equally in the phenotype. This is not relevant here since we are discussing non-allelic genes.
- **Incomplete dominance**: This is when the phenotype of heterozygotes is intermediate between those of the two homozygotes. Again, this does not apply as we are not dealing with alleles of the same gene.
- **Epistasis**: This is the phenomenon where the expression of one gene is suppressed or masked by another non-allelic gene.

4. **Defining Epistasis**:
- Epistasis can be classified into two types:
- **Dominant Epistasis**: The presence of a dominant epistatic gene masks the expression of another gene.
- **Recessive Epistasis**: The presence of a recessive epistatic gene masks the expression of another gene.

5. **Conclusion**: Based on the definitions and classifications, the correct answer to the question is **Epistasis**.

### Final Answer:
The failure of one gene to express in the presence of a non-allelic gene is known as **Epistasis**.

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