In a monohybrid cross , what will be a percentage of heterozygous offspring in `F_2` - generation?

Options

A. 0.25
B. 0.5
C. `12.5%`
D. `62.5%`

Answer

To solve the question about the percentage of heterozygous offspring in the F2 generation of a monohybrid cross, we can follow these steps:

### Step 1: Understand the Monohybrid Cross
In a monohybrid cross, we typically start with two parents that are homozygous for a trait. For example, let’s consider tallness (T) as the dominant trait and dwarfness (t) as the recessive trait. We can denote the parents as:
- Parent 1: Homozygous dominant (TT)
- Parent 2: Homozygous recessive (tt)

### Step 2: Create the F1 Generation
When these two parents are crossed, all offspring in the F1 generation will be heterozygous (Tt) because they inherit one allele from each parent. Therefore, the F1 generation consists entirely of Tt individuals.

### Step 3: Selfing the F1 Generation
Next, we self the F1 generation (Tt x Tt) to produce the F2 generation. We can use a Punnett square to visualize this cross:

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

### Step 4: Analyze the F2 Generation
From the Punnett square, we can see the genotypic ratio of the F2 generation:
- 1 TT (homozygous dominant)
- 2 Tt (heterozygous)
- 1 tt (homozygous recessive)

This gives us a genotypic ratio of 1:2:1.

### Step 5: Calculate the Percentage of Heterozygous Offspring
To find the percentage of heterozygous offspring (Tt) in the F2 generation:
- Total offspring = 1 (TT) + 2 (Tt) + 1 (tt) = 4
- Heterozygous offspring = 2 (Tt)

Now, we calculate the percentage:
\[ \text{Percentage of heterozygous offspring} = \left( \frac{\text{Number of heterozygous offspring}}{\text{Total offspring}} \right) \times 100 \]
\[ = \left( \frac{2}{4} \right) \times 100 = 50\% \]

### Conclusion
Thus, the percentage of heterozygous offspring in the F2 generation is **50%**.

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