The Terminator in transcription unit is located at

Options

A. 3' end downstream of the coding strand
B. 5' end downstream of the coding strand
C. 5' end upstream of the coding strand
D. 3' end upstream of the coding strand

Answer

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

### Step-by-Step Solution:

1. **Understanding the Transcription Unit**:
- A transcription unit consists of three main regions:
- **Promoter Region**: This is where RNA polymerase binds to initiate transcription.
- **Coding Region (Structural Gene)**: This is the part of the DNA that is transcribed into RNA.
- **Terminator Region**: This signals the end of transcription.

2. **Identifying the Orientation of DNA Strands**:
- DNA strands have a directionality, indicated as 5' (five prime) and 3' (three prime).
- The coding strand runs in the 5' to 3' direction.

3. **Locating the Terminator**:
- The terminator is located at the end of the transcription unit, specifically at the 3' end of the downstream strand of the coding region.
- This means that the terminator is found below the coding region in the downstream direction.

4. **Evaluating the Options**:
- The correct location of the terminator is at the **3' end of the downstream strand** of the coding strand.
- The other options (5' end downstream, 5' end upstream, and 3' upstream) do not accurately describe the position of the terminator.

5. **Conclusion**:
- Therefore, the terminator in a transcription unit is located at the **3' end of the downstream of the coding strand**.