Which of the following is a plasmid ?

Options

A. pBR 322
B. Bam HI
C. Sal I
D. Eco RI

Answer

To determine which of the given options is a plasmid, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of a Plasmid**:
- A plasmid is a small, circular, double-stranded DNA molecule that is distinct from a cell's chromosomal DNA. Plasmids are commonly found in bacteria and can replicate independently.

2. **Identify the Options**:
- The question provides four options, one of which is a plasmid. The options include PBR322 and three others that are likely restriction enzymes.

3. **Evaluate the First Option (PBR322)**:
- PBR322 is a well-known plasmid that was developed as a cloning vector. It was first used in 1977 by Herbert Boyer for genetic engineering purposes.

4. **Evaluate the Other Options**:
- The remaining three options are likely names of restriction enzymes. Restriction enzymes are proteins that cut DNA at specific sequences and are not plasmids.

5. **Conclude**:
- Since PBR322 is the only option that fits the definition of a plasmid, it is the correct answer.

### Final Answer:
The correct answer is **PBR322**, as it is a plasmid.

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