If the gene of interest is cloned at ECoRI in pBR322, the recombinant E-coli after transformation are

Options

A. Susceptible to ampicilin and tetracycline
B. Sensitive to tetracycline
C. Resistant to kanamycin
D. Resistant to ampicilin and tetracycline

Answer

To solve the question regarding the recombinant E. coli after transformation with a gene of interest cloned at the ECoRI site in pBR322, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Vector (pBR322)**:
- pBR322 is a plasmid vector used for cloning. It contains genes that confer resistance to antibiotics, specifically ampicillin and tetracycline.

2. **Identify the Cloning Site**:
- The question specifies that the gene of interest is cloned at the ECoRI site of pBR322. This is important because the location of the insertion can affect the antibiotic resistance of the transformed bacteria.

3. **Analyze the Resistance Genes**:
- The pBR322 plasmid has two antibiotic resistance genes:
- **Ampicillin resistance (bla)**: Located in one region of the plasmid.
- **Tetracycline resistance (tet)**: Located in another region of the plasmid.

4. **Insertion at ECoRI**:
- When the gene of interest is inserted at the ECoRI site, it does not disrupt the ampicillin or tetracycline resistance genes. This means that the plasmid retains its ability to confer resistance to both antibiotics.

5. **Transformation of E. coli**:
- After the transformation, the recombinant E. coli will carry the pBR322 plasmid with the inserted gene. Since the resistance genes are intact, the transformed E. coli will be resistant to both ampicillin and tetracycline.

6. **Conclusion**:
- Therefore, the recombinant E. coli after transformation will be resistant to both ampicillin and tetracycline.

### Final Answer:
The correct option is **D: resistant to ampicillin and tetracycline**.