Which of the following is not a feature of the plasmids?

Options

A. Transferable
B. Single--stranded
C. Independent replication
D. Circular structure

Answer

### Step-by-Step Solution:

1. **Understanding Plasmids**:
- Plasmids are small, extra-chromosomal DNA molecules found in bacteria. They are distinct from chromosomal DNA and can replicate independently.

2. **Features of Plasmids**:
- **Extra-chromosomal DNA**: Plasmids exist outside the main bacterial chromosome.
- **Origin of Replication**: They possess their own origin of replication, allowing them to replicate independently within the cell.
- **Selectable Markers**: Many plasmids carry genes that provide resistance to antibiotics, which can be used as selectable markers in genetic engineering.
- **Double-stranded Structure**: Plasmids are typically double-stranded DNA molecules.
- **Circular Structure**: Most plasmids have a circular shape.
- **Transferability**: Plasmids can transfer genes between bacteria, which is important for horizontal gene transfer.

3. **Identifying the Incorrect Feature**:
- Among the features listed, the statement that plasmids are "single-stranded" is incorrect. Plasmids are double-stranded DNA molecules.

4. **Conclusion**:
- Therefore, the feature that is **not** characteristic of plasmids is that they are single-stranded.

### Final Answer:
The feature that is not characteristic of plasmids is that they are **single-stranded**.

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