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:

1. **YAC (Yeast Artificial Chromosome)**:
- YACs are cloning vectors that are used for cloning DNA fragments in yeast. They contain essential elements such as telomeric sequences and centromeres, allowing them to replicate within yeast cells. Thus, YAC is a cloning vector.

2. **Ti (Tumor Inducing) Plasmid**:
- The Ti plasmid is derived from Agrobacterium tumefaciens and is used as a vector for transferring genes into plants. It is specifically designed for plant genetic engineering. Therefore, Ti is also a cloning vector.

3. **PBR322**:
- PBR322 is a well-known plasmid used in recombinant DNA technology. It is commonly used as a cloning vector in various organisms. Thus, PBR322 is a cloning vector.

4. **Ri (Root Inducing) Plasmid**:
- The Ri plasmid is also found in Agrobacterium but is associated with inducing hairy root disease in plants. Unlike Ti, it is not typically used as a cloning vector for genetic engineering purposes. Therefore, Ri is not a cloning vector.

Based on the analysis above, the answer to the question "Which among the following is not a plasmid cloning vector?" is **Ri**.

### Summary of Steps:
1. Identify each option and its function.
2. Determine if each option is a cloning vector.
3. Conclude which option is not a cloning vector.