A gene that takes part in synthesis of polypeptide is
(a) Structural gene
(b) Regulator gene
(c) Operator gene
(d) Leading strand

Options

A. Structural gene
B. Regulator gene
C. Operator gene
D. Leading strand

Answer

To solve the question "A gene that takes part in the synthesis of polypeptide is", we need to analyze the options provided:

1. **Structural Gene**:
- Structural genes are responsible for coding for proteins. They undergo transcription to produce mRNA, which is then translated to synthesize polypeptides (proteins). Thus, structural genes directly participate in polypeptide synthesis.

2. **Regulator Gene**:
- Regulator genes do not code for proteins themselves; instead, they produce products (like regulatory proteins) that control the expression of structural genes. Therefore, they do not directly participate in the synthesis of polypeptides.

3. **Operator Gene**:
- The operator is a segment of DNA that a repressor protein can bind to, inhibiting the transcription of adjacent structural genes. It plays a regulatory role but does not directly participate in the synthesis of polypeptides.

4. **Leading Strand**:
- The leading strand refers to the strand of DNA that is synthesized continuously during DNA replication. It is not involved in polypeptide synthesis.

Based on this analysis, the correct answer is:

**(a) Structural gene**

### Step-by-Step Solution:
1. **Identify the question**: Determine what type of gene is involved in the synthesis of polypeptides.
2. **Evaluate each option**:
- **Structural Gene**: Understand that this type of gene codes for proteins and is involved in polypeptide synthesis.
- **Regulator Gene**: Recognize that this gene regulates other genes but does not code for polypeptides.
- **Operator Gene**: Acknowledge that this gene is involved in controlling gene expression but does not synthesize polypeptides.
- **Leading Strand**: Realize that this term refers to DNA replication and is not related to polypeptide synthesis.
3. **Select the correct answer**: Conclude that the structural gene is the one that participates in polypeptide synthesis.