In a transcription unit the terminator is located towards

Options

A. 3. - end of coding strand
B. 5. - end of coding strand
C. 3. - end of template strand
D. Upstream of the structural gene

Answer

To solve the question regarding the location of the terminator in a transcription unit, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components of a Transcription Unit**:
- A transcription unit consists of a promoter, a coding region (structural gene), and a terminator. The promoter is where transcription begins, the coding region is where the RNA is synthesized, and the terminator signals the end of transcription.

2. **Identify the Directionality of DNA Strands**:
- DNA strands have directionality: one end is referred to as the 5' end and the other as the 3' end. The coding strand (also known as the non-template strand) runs from 5' to 3', while the template strand runs from 3' to 5'.

3. **Locate the Terminator**:
- The terminator is located at the end of the transcription unit. It is positioned downstream of the coding region. This means it is found at the 3' end of the coding strand.

4. **Evaluate the Options**:
- Option 1: The 3' end of the coding strand - This is correct as the terminator is located here.
- Option 2: The 5' end of the coding strand - This is incorrect because the terminator is not at the start of transcription.
- Option 3: The 3' end of the template strand - This is incorrect because the terminator is not located on the template strand.
- Option 4: Upstream of the structural gene - This is incorrect because the terminator is downstream, not upstream.

5. **Conclusion**:
- Based on the analysis, the correct answer is that the terminator is located at the 3' end of the coding strand.

### Final Answer:
The terminator is located at the **3' end of the coding strand**.

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