Termination of transcription is by

Options

A. Only `rho` factor
B. Only `sigma` factor
C. RNA polymerase when associated with `rho` factor
D. RNA polymerase when associated with `sigma` factor

Answer

### Step-by-Step Solution:

1. **Understanding Transcription**: Transcription is the process by which RNA is synthesized from a DNA template. This process involves several stages: initiation, elongation, and termination.

2. **Identifying Factors Involved**: During transcription, different factors play roles at various stages. The sigma factor is important for the initiation of transcription as it helps RNA polymerase bind to the promoter region of the DNA.

3. **Role of the Rho Factor**: The Rho factor is a protein that is specifically involved in the termination of transcription in prokaryotes. It binds to the RNA transcript and facilitates the release of the RNA polymerase from the DNA template once the transcription is complete.

4. **Termination Mechanism**: The termination of transcription can occur through two mechanisms: Rho-dependent and Rho-independent. In Rho-dependent termination, the Rho factor binds to the RNA strand and moves along it until it catches up with the RNA polymerase, causing it to detach from the DNA.

5. **Conclusion**: Based on the roles of the sigma factor and the Rho factor, we conclude that the termination of transcription is primarily mediated by the Rho factor. Therefore, the correct answer to the question is that termination of transcription is by the Rho factor.

### Final Answer:
Termination of transcription is by the Rho factor.

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