The promoter site and the terminator site for transcription are located at:

Options

A. 3' (downstream) end and 5' (upstream) end, respectively of the transcription unit
B. 5' (upstream) end and 3' (downstream) end, respectively of the transcription unit
C. the 5' (upstream) end of the transcription unit
D. the 3' (downstream) end of the transcription unit

Explanation

To answer the question regarding the location of the promoter site and the terminator site for transcription, we can break down the information step by step.

### Step-by-Step Solution:

1. **Understanding Transcription**:
- Transcription is the process where the DNA sequence is copied into RNA. This process involves the enzyme RNA polymerase, which synthesizes RNA from the DNA template.

2. **Defining the Transcription Unit**:
- A transcription unit consists of the DNA sequence that is transcribed into RNA. It includes the promoter, the coding region, and the terminator.

3. **Identifying the Promoter Site**:
- The promoter is a specific region of DNA that initiates transcription. It is located upstream of the coding sequence, which means it is found towards the 5' end of the DNA strand. This is where RNA polymerase binds to start the transcription process.

4. **Identifying the Terminator Site**:
- The terminator is a sequence of DNA that signals the end of transcription. It is located downstream of the coding region, meaning it is found towards the 3' end of the DNA strand. This is where RNA polymerase stops transcription.

5. **Conclusion**:
- Therefore, the promoter site is located at the 5' upstream position, and the terminator site is located at the 3' downstream position relative to the transcription unit.

### Final Answer:
The promoter site and the terminator site for transcription are located at **5' upstream and 3' downstream**, respectively.

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