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' (uptream) end
D. the 3' (downstream)end

Explanation

To answer the question regarding the locations of the promoter site and the terminator site for transcription, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Transcription**: Transcription is the process of synthesizing RNA from a DNA template. This process involves specific sites on the DNA where transcription begins and ends.

2. **Identify the Promoter Site**: The promoter is a specific region on the DNA that serves as the binding site for RNA polymerase, the enzyme responsible for synthesizing RNA. The promoter is located upstream of the structural gene, which means it is found towards the 5' end of the coding strand.

3. **Identify the Terminator Site**: The terminator is a sequence of DNA that signals the end of transcription. It is located downstream of the structural gene, which means it is found towards the 3' end of the coding strand.

4. **Relate Promoter and Terminator Locations**: Since the promoter is at the 5' end (upstream) and the terminator is at the 3' end (downstream), we can conclude that the promoter and terminator sites are located at the 5' and 3' ends, respectively, of the transcription unit.

5. **Select the Correct Option**: Based on the understanding that the promoter is at the 5' end and the terminator is at the 3' end, the correct answer to the question is option 2: "5' and 3' respectively of the transcription unit."

### Final Answer:
The promoter site and the terminator site for transcription are located at the 5' and 3' ends, respectively, of the transcription unit.

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