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 the Monohybrid Cross**:
In a monohybrid cross, we are examining the inheritance of a single trait. For example, let’s consider a trait for plant height where "T" represents the dominant tall allele and "t" represents the recessive dwarf allele.

2. **Identify the Parent Generation (P Generation)**:
We start with two purebred parents. One parent is homozygous tall (TT) and the other is homozygous dwarf (tt).

3. **Determine the F1 Generation**:
When we cross the two parents (TT x tt), all offspring in the F1 generation will be heterozygous (Tt), displaying the dominant phenotype (tall).

4. **Self-Cross the F1 Generation**:
Next, we self-cross the F1 generation (Tt x Tt) to produce the F2 generation.

5. **Create a Punnett Square**:
To find the genotypes of the F2 generation, we can set up a Punnett square:
```
T | t
-----------------
T | TT | Tt
-----------------
t | Tt | tt
```

6. **Count the Genotypes**:
From the Punnett square, we can see the following genotypes:
- 1 TT (homozygous tall)
- 2 Tt (heterozygous tall)
- 1 tt (homozygous dwarf)

7. **Write the Genotypic Ratio**:
The genotypic ratio for the F2 generation is:
- 1 TT : 2 Tt : 1 tt

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

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