The `F_2` genotypic ratio of monohybrid cross is

Options

A. `1:1`
B. `1:2:1`
C. `2:1:2`
D. `9:3:3:1`

Answer

To determine the F2 genotypic ratio 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 controlled by two alleles. For example, consider a cross between a homozygous tall plant (TT) and a homozygous dwarf plant (tt).

2. **Determine the F1 Generation**: The F1 generation results from the cross of the two parents. In our example:
- Parent 1 (Tall): TT
- Parent 2 (Dwarf): tt
- F1 Generation: All offspring will be heterozygous (Tt).

3. **Selfing the F1 Generation**: To obtain the F2 generation, we will self-fertilize the F1 plants (Tt x Tt).

4. **Gamete Formation**: Each F1 plant can produce two types of gametes: T and t.

5. **Punnett Square**: Set up a Punnett square to visualize the possible combinations of gametes from the F1 generation:
```
T t
----------------
T | TT | Tt |
----------------
t | Tt | tt |
----------------
```

6. **Count the Genotypes**: From the Punnett square, we can see the resulting genotypes:
- TT: 1
- Tt: 2
- tt: 1

7. **F2 Genotypic Ratio**: The genotypic ratio of the F2 generation is therefore:
- TT : Tt : tt = 1 : 2 : 1

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

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