Which among the following is not a plasmid (cloning vec- tor)?

Options

A. YAC
B. Ti
C. pBR322
D. Ri

Answer

To determine which among the given options is not a plasmid (cloning vector), we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Plasmids**:
- Plasmids are small, circular DNA molecules that can replicate independently of chromosomal DNA. They are often used as vectors to transfer genetic material into cells.

2. **Analyzing the Options**:
- **Option 1: YAC (Yeast Artificial Chromosome)**:
- YAC is a cloning vector used in yeast. It contains essential elements such as telomeric sequences, a centromere, and replication origins. Therefore, YAC is a cloning vector.

- **Option 2: Ti Plasmid**:
- Ti plasmid is derived from *Agrobacterium tumefaciens* and is known for inducing tumors in plants. It is widely used as a vector for transferring genes into plant cells. Hence, Ti plasmid is also a cloning vector.

- **Option 3: PBR 322**:
- PBR 322 is one of the first plasmids used in recombinant DNA technology. It contains antibiotic resistance genes and is commonly used as a cloning vector. Thus, PBR 322 is a cloning vector as well.

- **Option 4: R.I. Plasmid**:
- R.I. plasmids (Root Inducing plasmids) are also derived from *Agrobacterium* and are responsible for inducing hairy root disease in plants. However, they are not used as cloning vectors in genetic engineering.

3. **Conclusion**:
- After analyzing all the options, we find that the only option that is not a plasmid used as a cloning vector is **Option 4: R.I. Plasmid**.

### Final Answer:
- The correct answer is **Option 4: R.I. Plasmid**.