Identify the cross in which the genotypic ratio of `F_(2)` is 1:2:1

Options

A. Monohybrid cross
B. Codominance
C. Incomplete dominance
D. All these

Answer

To identify the cross in which the genotypic ratio of the F2 generation is 1:2:1, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Parental Generation (P Generation)**:
- We start with two pure breeding plants. Let's denote them as:
- Tall plant: TT (homozygous dominant)
- Dwarf plant: tt (homozygous recessive)

2. **Determine the F1 Generation**:
- When we cross the parental generation (TT x tt), all offspring in the F1 generation will be heterozygous (Tt).
- Thus, the F1 generation consists of 100% Tt (tall).

3. **Self-Pollination of F1 Generation**:
- To find the F2 generation, we need to self-pollinate the F1 generation (Tt x Tt).
- The gametes produced by each Tt plant will be T and t.

4. **Set Up the Punnett Square**:
- Create a Punnett square to visualize the possible combinations of gametes:
```
T t
-----------
T | TT | Tt |
-----------
t | Tt | tt |
-----------
```

5. **Analyze the F2 Generation Results**:
- From the Punnett square, we can see the genotypes of the F2 generation:
- 1 TT (homozygous dominant)
- 2 Tt (heterozygous)
- 1 tt (homozygous recessive)

6. **Calculate the Genotypic Ratio**:
- The genotypic ratio of the F2 generation is:
- 1 TT : 2 Tt : 1 tt
- This confirms that the genotypic ratio is 1:2:1.

7. **Conclusion**:
- The cross that results in a genotypic ratio of 1:2:1 in the F2 generation is a **monohybrid cross**.

### Final Answer:
The cross in which the genotypic ratio of F2 is 1:2:1 is a **monohybrid cross**.

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