In `F_(2)` generation of monohybrid cross the cause of 1: 2:1 phenotypic ratio is

Options

A. Inhibition
B. Epistatics
C. Incomplete dominance
D. Quantitative inheritance

Explanation

To solve the question regarding the cause of the 1:2:1 phenotypic ratio in the F2 generation of a monohybrid cross, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Monohybrid Cross**: A monohybrid cross involves a single trait that is being studied, where one parent is homozygous dominant (AA) and the other is homozygous recessive (aa). The F1 generation will all be heterozygous (Aa).

2. **F1 Generation**: In the F1 generation, all offspring (Aa) will exhibit the dominant phenotype. This means that if we were looking at flower color, for example, all flowers in the F1 generation would display the dominant color.

3. **F2 Generation**: When the F1 individuals (Aa) are crossed with each other (Aa x Aa), we can use a Punnett square to determine the genotypes of the F2 generation.

4. **Punnett Square Analysis**: The Punnett square for the cross Aa x Aa will yield the following genotypes:
- AA (homozygous dominant)
- Aa (heterozygous)
- Aa (heterozygous)
- aa (homozygous recessive)

This results in the genotypic ratio of 1 AA : 2 Aa : 1 aa.

5. **Phenotypic Ratio**: In the case of incomplete dominance, the phenotypes of the offspring will reflect this genotypic ratio. The phenotypic ratio will also be 1:2:1, where:
- 1 exhibits the dominant phenotype (AA)
- 2 exhibit an intermediate phenotype (Aa)
- 1 exhibits the recessive phenotype (aa)

6. **Conclusion**: The 1:2:1 phenotypic ratio in the F2 generation is due to incomplete dominance, where the heterozygous phenotype is distinct from both homozygous phenotypes.

### Final Answer:
The cause of the 1:2:1 phenotypic ratio in the F2 generation of a monohybrid cross is **incomplete dominance**.

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