Transcription by structural genes is catalysed by enzyme

Options

A. RNase
B. RNA polymerase
C. DNA polymerase
D. Nuclease

Answer

To solve the question regarding which enzyme catalyzes transcription by structural genes, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Process of Transcription**:
- Transcription is the biological process where the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). This process is essential for gene expression.

2. **Identify the Enzymes Involved**:
- The key enzyme that facilitates this process is crucial for the conversion of DNA to RNA.

3. **Evaluate the Options**:
- **Option A: RNA** - This is not an enzyme; rather, it is the product of transcription.
- **Option B: RNA polymerase** - This is the enzyme that catalyzes the transcription of DNA into RNA.
- **Option C: DNA polymerase** - This enzyme is involved in DNA replication, not transcription.
- **Option D: Nucleus** - This is the cellular organelle where transcription occurs, but it is not an enzyme.

4. **Select the Correct Answer**:
- Based on the evaluation, the enzyme that catalyzes transcription by structural genes is **RNA polymerase**.

5. **Final Answer**:
- The correct answer is **Option B: RNA polymerase**.