Find the true statement from the following

Options

A. Ori means origin of transcription.
B. Some bacterial cell may have copy number of plasmid that varies from 15 - 100.
C. Vector should have many recognition sites for commonly used restriction enzymes so that alien DNA can attach to any one of the sites easily.
D. An ideal vector should have ori, site restriction site for different REN but not a selectable marker.

Answer

To solve the question, "Find the true statement from the following," we need to analyze each option provided and determine which one is correct based on our understanding of molecular biology concepts, particularly in the context of vectors and plasmids.

### Step-by-Step Solution:

1. **Understanding the Options**:
- **Option 1**: "Ori means origin of transcription."
- **Option 2**: "Some bacterial cells may have a copy number of plasmid that varies from 15 to 100."
- **Option 3**: "Vector should have many recognition sites for commonly used restriction enzymes so that alien DNA can attach to any one of the sites easily."
- **Option 4**: "An ideal vector should have ORI site restriction for different REN but not a selectable marker."

2. **Analyzing Option 1**:
- The term "Ori" refers to the "Origin of Replication," not transcription. This statement is incorrect.

3. **Analyzing Option 2**:
- It is known that some bacterial cells can indeed have a copy number of plasmids that varies significantly, often ranging from 15 to 100 copies per cell. This statement is correct.

4. **Analyzing Option 3**:
- Vectors should ideally have a single recognition site for restriction enzymes to avoid generating multiple fragments, which complicates cloning. Therefore, this statement is incorrect.

5. **Analyzing Option 4**:
- An ideal vector must have a selectable marker to distinguish between transformed and non-transformed cells. Thus, this statement is also incorrect.

6. **Conclusion**:
- After analyzing all options, the only true statement is **Option 2**: "Some bacterial cells may have a copy number of plasmid that varies from 15 to 100."

### Final Answer:
The true statement is: **Option 2** - "Some bacterial cells may have a copy number of plasmid that varies from 15 to 100."