What will be the distribution of phenotypic features in the first generation after a cross between a homozygous female and a heterozygous male for a single locus ?

Options

A. `3:1`
B. `1: 2: 1`
C. `1: 1`
D. none of these

Explanation

To determine the distribution of phenotypic features in the first generation after a cross between a homozygous female and a heterozygous male for a single locus, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Genotypes of the Parents:**
- The homozygous female can be represented as **TT** (homozygous dominant).
- The heterozygous male can be represented as **Tt** (heterozygous).

2. **Set Up the Punnett Square:**
- To visualize the potential offspring, we can create a Punnett square. The rows will represent the alleles from the female (TT), and the columns will represent the alleles from the male (Tt).

```
T T
__________
T | TT | TT |
|______|______|
t | Tt | Tt |
|______|______|
```

3. **Determine the Genotypes of the Offspring:**
- From the Punnett square, the possible genotypes of the offspring are:
- TT (homozygous dominant)
- TT (homozygous dominant)
- Tt (heterozygous)
- Tt (heterozygous)

4. **Identify the Phenotypes:**
- The phenotypes corresponding to the genotypes are:
- TT and Tt both express the dominant trait (let's say "tall").
- Therefore, all offspring will exhibit the tall phenotype.

5. **Calculate the Phenotypic Ratio:**
- Since all offspring are tall, the phenotypic ratio is:
- Tall: 4 (TT and Tt)
- Dwarf: 0
- Thus, the ratio of tall to dwarf is 4:0, which can also be simplified to a ratio of 1:1 when only considering the presence of the dominant phenotype.

6. **Conclusion:**
- The distribution of phenotypic features in the first generation after the cross will be a ratio of 1:1 for tall to dwarf, where tall is dominant.

### Final Answer:
The distribution of phenotypic features in the first generation after the cross between a homozygous female (TT) and a heterozygous male (Tt) will be in the ratio of **1:1** (tall to dwarf).