The genotypic ratio of a monohybrid cross will be

Options

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

Answer

To determine the genotypic ratio of a monohybrid cross, we can follow these steps:

### Step-by-Step Solution:

1. **Define Monohybrid Cross**:
A monohybrid cross involves a single trait where two parents differ in one characteristic. For example, we can consider the height of plants, where one parent is tall (dominant trait) and the other is dwarf (recessive trait).

2. **Identify Genotypes**:
- Let’s denote the tall plant genotype as **TT** (homozygous dominant) and the dwarf plant genotype as **tt** (homozygous recessive).

3. **Gamete Formation**:
- The tall plant (TT) can only produce gametes with the allele **T**.
- The dwarf plant (tt) can only produce gametes with the allele **t**.

4. **F1 Generation**:
- When we cross the tall plant (TT) with the dwarf plant (tt), all offspring (F1 generation) will have the genotype **Tt** (heterozygous).

5. **Self-Pollination of F1 Generation**:
- Now, we self-pollinate the F1 generation (Tt x Tt). The gametes produced by Tt will be **T** and **t**.

6. **Punnett Square**:
- Set up a Punnett square to find the F2 generation:
```
T t
------------
T | TT | Tt |
------------
t | Tt | tt |
```

7. **F2 Generation Genotypes**:
- From the Punnett square, we find the genotypes of the F2 generation:
- **TT**: 1
- **Tt**: 2
- **tt**: 1

8. **Genotypic Ratio**:
- The genotypic ratio of the offspring in the F2 generation is **1 TT : 2 Tt : 1 tt**.

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

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