Which of the following is correct about pBR322 ?

Options

A. ori - original restriction endonuclease
B. rop - codes for proteins that help in replication
C. Hind III and EcoRI - Selectable markers
D. `tet^(R)` - gene that makes bacterium sensitive to tetracycline

Answer

To determine which statement is correct about pBR322, we need to analyze each of the provided options based on our understanding of pBR322's structure and function.

### Step-by-Step Solution:

1. **Understanding pBR322**:
- pBR322 is an artificial plasmid vector developed by Bolivar and Rodriguez in 1977. It is widely used in molecular cloning.

2. **Analyzing the Statements**:
- **Statement A**: "ORI Original Restriction Endonuclease"
- **Analysis**: ORI stands for "Origin of Replication," not "Original Restriction Endonuclease." This statement is incorrect.

- **Statement B**: "ROP Codes for Proteins Help in Replication"
- **Analysis**: The ROP region indeed codes for proteins that assist in the replication of the plasmid. This statement is correct.

- **Statement C**: "Hind III and Eco R1 Selectable Markers"
- **Analysis**: Hind III and Eco R1 are restriction sites where specific restriction endonucleases cut the DNA. They are not selectable markers. This statement is incorrect.

- **Statement D**: "Tetracycline Gene that Makes Bacterium Sensitive to Tetracycline"
- **Analysis**: The tetracycline gene provides resistance to tetracycline, not sensitivity. Therefore, this statement is also incorrect.

3. **Conclusion**:
- The only correct statement about pBR322 is **Statement B**: "ROP Codes for Proteins Help in Replication."

### Final Answer:
**B. ROP Codes for Proteins Help in Replication**

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