What will be genotypic ratio in the `F_(2)` generation of a monohybrid cross ?

Options

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

Answer

To find the genotypic ratio in the F2 generation of a monohybrid cross, we can follow these steps:

### Step 1: Understand the Monohybrid Cross
A monohybrid cross involves one trait, where one allele is dominant over the other. For example, let's consider plant height where:
- Tall (T) is dominant
- Dwarf (t) is recessive

### Step 2: Determine the Parental Generation (P Generation)
In the P generation, we cross two purebred plants:
- One pure tall plant (TT)
- One pure dwarf plant (tt)

### Step 3: Determine the F1 Generation
When we cross the P generation (TT x tt), all offspring in the F1 generation will be heterozygous (Tt) and exhibit the dominant trait (tall).

### Step 4: Selfing the F1 Generation to Produce F2
To produce the F2 generation, we self-cross the F1 generation:
- Tt x Tt

### Step 5: Gamete Formation
Each parent (Tt) can produce two types of gametes:
- T (dominant)
- t (recessive)

### Step 6: Create a Punnett Square
Now, we can set up a Punnett square to determine the genotypes of the F2 generation:
```
T t
----------------
T | TT | Tt |
----------------
t | Tt | tt |
----------------
```

### Step 7: Analyze the Results
From the Punnett square, we can see the genotypes of the offspring:
- 1 TT (homozygous dominant)
- 2 Tt (heterozygous)
- 1 tt (homozygous recessive)

### Step 8: Calculate the Genotypic Ratio
The genotypic ratio in the F2 generation is:
- 1 TT : 2 Tt : 1 tt

Thus, the genotypic ratio is **1:2:1**.

### Conclusion
The genotypic ratio in the F2 generation of a monohybrid cross is **1:2:1**.

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