A gene is said to be dominant, if

Options

A. It express it's effect only in homozygous stage
B. It expressed only in heterozygous condition
C. It expressed both in homozygous and heterozygous condition
D. It never expressed in any condition

Answer

To determine when a gene is said to be dominant, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Genes and Alleles**:
- A gene is the basic unit of heredity and is responsible for inheritance and genetics. It is located on chromosomes and exists in different forms known as alleles.

2. **Defining Alleles**:
- Alleles are variant forms of a gene. For example, a gene may have a dominant allele (represented as a capital letter, e.g., A) and a recessive allele (represented as a lowercase letter, e.g., a).

3. **Dominant vs. Recessive Alleles**:
- A dominant allele expresses its trait in both homozygous (AA) and heterozygous (Aa) conditions. This means that if at least one dominant allele is present, the dominant trait will be expressed.
- In contrast, a recessive allele only expresses its trait in the homozygous condition (aa). It does not show its effect in the presence of a dominant allele.

4. **Example**:
- Consider the alleles A (dominant) and a (recessive). In a heterozygous condition (Aa), the presence of A will mask the effect of a. Therefore, the phenotype will reflect the dominant trait.

5. **Conclusion**:
- A gene is said to be dominant if it is expressed in both homozygous and heterozygous conditions. Therefore, the correct answer to the question is that a gene is dominant when it shows its effect regardless of whether it is in a homozygous or heterozygous state.

### Final Answer:
A gene is said to be dominant if it is expressed in both homozygous and heterozygous conditions.

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