Which one of the following is a correct statement ?

Options

A. Dominant trait can be expressed in homozygous condition only
B. Recessive condition is expressed in homozygous condition only
C. Dominant condition cannot be expressed in homozygous condition
D. All of the above

Answer

To solve the question "Which one of the following is a correct statement?", we will analyze the statements provided regarding dominant and recessive traits.

### Step-by-Step Solution:

1. **Understanding Alleles**:
- Alleles are different forms of a gene that can exist at a specific locus on a chromosome. They can be dominant or recessive.
- Dominant alleles mask the effect of recessive alleles when present.

**Hint**: Remember that alleles are variations of a gene that determine traits.

2. **Homozygous and Heterozygous Conditions**:
- An individual is **homozygous** for a trait if it has two identical alleles (e.g., AA or aa).
- An individual is **heterozygous** if it has two different alleles (e.g., Aa).

**Hint**: Homozygous means "same alleles," while heterozygous means "different alleles."

3. **Expression of Dominant Traits**:
- A dominant trait can be expressed in both homozygous (AA) and heterozygous (Aa) conditions.
- Therefore, the statement "dominant trait can be expressed in homozygous" is true, but it can also be expressed in heterozygous.

**Hint**: Dominant traits show their effect even when only one dominant allele is present.

4. **Expression of Recessive Traits**:
- A recessive trait is only expressed when an individual is homozygous for that trait (aa). In a heterozygous condition (Aa), the dominant allele masks the recessive allele.

**Hint**: Recessive traits require two copies (homozygous) to be expressed.

5. **Evaluating the Statements**:
- **Statement 1**: "Dominant trait can be expressed in homozygous" - This is correct.
- **Statement 2**: "Recessive condition is expressed only in the homozygous condition" - This is also correct.
- **Statement 3**: "Dominant condition cannot be expressed in homozygous condition" - This is incorrect because dominant traits can be expressed in homozygous conditions.
- **Statement 4**: "All of the above" - This is incorrect as not all statements are true.

6. **Conclusion**:
- The correct statement is that a recessive condition is expressed only in the homozygous condition. The dominant trait can be expressed in both homozygous and heterozygous conditions.

### Final Answer:
The correct statement is: "Recessive condition is expressed only in the homozygous condition."