Percentage of pure individuals in `F_(2)` of a monohybrid cross

Options

A. 100
B. 75
C. 50
D. 25

Answer

To find the percentage of pure individuals in the F2 generation of a monohybrid cross, we can follow these steps:

### Step 1: Understand the Monohybrid Cross
A monohybrid cross involves a single trait, where we typically look at two contrasting traits. For example, we can consider a cross between tall (dominant) and dwarf (recessive) plants.

### Step 2: Define the Genotypes
Let’s assign the following genotypes:
- Tall (dominant) = TT (homozygous)
- Dwarf (recessive) = tt (homozygous)

### Step 3: Perform the F1 Generation Cross
When we cross TT (tall) with tt (dwarf), the F1 generation will all be heterozygous (Tt), which will express the dominant trait (tall).

### Step 4: Selfing the F1 Generation
To obtain the F2 generation, we perform selfing of the F1 plants:
- Tt x Tt

### Step 5: Create a Punnett Square
We can create a Punnett square to predict the genotypes of the F2 generation:

```
T t
----------------
T | TT | Tt |
----------------
t | Tt | tt |
----------------
```

### Step 6: Analyze the Results
From the Punnett square, we can see the following genotypes in the F2 generation:
- 1 TT (homozygous tall)
- 2 Tt (heterozygous tall)
- 1 tt (homozygous dwarf)

### Step 7: Calculate the Percentage of Pure Individuals
The pure individuals (homozygous) in the F2 generation are TT and tt. Therefore, we have:
- Total pure individuals = 1 (TT) + 1 (tt) = 2
- Total individuals = 4 (TT, Tt, Tt, tt)

The percentage of pure individuals is calculated as follows:
\[ \text{Percentage of pure individuals} = \left( \frac{\text{Number of pure individuals}}{\text{Total individuals}} \right) \times 100 = \left( \frac{2}{4} \right) \times 100 = 50\% \]

### Conclusion
Thus, the percentage of pure individuals in the F2 generation of a monohybrid cross is **50%**.

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