Gene which is responsible for the synthesis of a polypeptide chain is called :-

Options

A. Promotor gene
B. Structural gene
C. Regulator gene
D. Operator gene

Answer

To answer the question "Gene which is responsible for the synthesis of a polypeptide chain is called:", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the type of gene that is responsible for synthesizing a polypeptide chain. This involves knowing the different types of genes and their functions.

2. **Identifying Gene Types**:
- **Promoter Gene**: This is a DNA segment that initiates the transcription of a gene. It is not responsible for the synthesis of the polypeptide chain itself.
- **Regulator Gene**: This gene regulates the expression of other genes, particularly structural genes, through the production of proteins like transcription factors. It does not directly code for polypeptides.
- **Operator Gene**: This is a DNA sequence that acts as a binding site for repressor proteins, preventing transcription. It does not code for polypeptides.
- **Structural Gene**: This gene codes for the actual polypeptide chain. It contains the information needed to produce proteins.

3. **Conclusion**: Based on the definitions, the gene responsible for the synthesis of a polypeptide chain is the **Structural Gene**.

4. **Final Answer**: The correct answer is **Structural Gene**.