Which of the following steps in transcription is catalysed by RNA polymerase?

Options

A. Initiation
B. Elongation
C. Terminatioin
D. All of the above

Explanation

**Step-by-Step Solution:**

1. **Understanding Transcription**: Transcription is the process where the DNA sequence is copied into RNA. It involves three main steps: initiation, elongation, and termination.

2. **Identifying the Role of RNA Polymerase**: RNA polymerase is the enzyme responsible for catalyzing the transcription process. It synthesizes RNA from the DNA template.

3. **Breaking Down the Steps of Transcription**:
- **Initiation**: This is the first step where RNA polymerase binds to the promoter region of the DNA and unwinds the DNA strands.
- **Elongation**: In this step, RNA polymerase moves along the DNA template strand, adding RNA nucleotides in a 5' to 3' direction, thus elongating the RNA strand.
- **Termination**: This is the final step where RNA polymerase reaches a termination signal and releases the newly synthesized RNA strand.

4. **Determining the Step Catalyzed by RNA Polymerase**: Among the three steps of transcription, RNA polymerase primarily catalyzes the elongation of the RNA strand. It is responsible for the polymerization of RNA nucleotides during this phase.

5. **Conclusion**: Therefore, the step in transcription that is catalyzed by RNA polymerase is the **elongation** step.

**Final Answer**: The step in transcription that is catalyzed by RNA polymerase is **elongation**.

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