`F_(2)` generation has genotypic and phenotypic ratio of 1:2:1. It is

Options

A. Codominance
B. Dihybrid cross
C. Monohybrid cross with complete dominance
D. Monohybrid cross with incomplete dominance.

Answer

To solve the question regarding the F2 generation having a genotypic and phenotypic ratio of 1:2:1, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Ratios**: The question states that the F2 generation has both a genotypic and phenotypic ratio of 1:2:1. This indicates that there are three different genotypes and phenotypes represented in the offspring.

2. **Identifying the Type of Inheritance**: The 1:2:1 ratio is characteristic of incomplete dominance in a monohybrid cross. In incomplete dominance, the dominant allele does not completely mask the effects of the recessive allele, resulting in a third phenotype that is a blend of the two.

3. **Example of Incomplete Dominance**: A classic example of incomplete dominance is the flower color in the Mirabilis jalapa (four o'clock plant). In this case:
- Red flowers (RR) are homozygous dominant.
- White flowers (rr) are homozygous recessive.
- When these are crossed (RR x rr), the F1 generation will all be heterozygous (Rr), which will exhibit a pink phenotype.

4. **Selfing the F1 Generation**: When the F1 generation (Rr) is self-fertilized (Rr x Rr), the resulting F2 generation will have the following genotypes:
- 1 RR (red)
- 2 Rr (pink)
- 1 rr (white)
This gives us the genotypic ratio of 1:2:1.

5. **Conclusion**: Since both the genotypic and phenotypic ratios are 1:2:1, we conclude that the F2 generation is a result of a monohybrid cross exhibiting incomplete dominance.

### Final Answer:
The F2 generation with a genotypic and phenotypic ratio of 1:2:1 is a result of **monohybrid cross with incomplete dominance**.

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