A plasmid has two antibiotic-resistance genes, one for ampicillin and one for tetracycline. It is treated with a restriction enzyme that cuts in the middle of the ampicillin gene. DNA fragments containing a haemoglobin gene were cut with the same enzyme. The plasmids and fragments are mixed, treated with ligase and used to transform bacterial cells. Clones that have taken up the recombinant DNA are the one that

Options

A. are blue and can grow on plates with both antibiotics
B. can grow on plates with ampicillin, but not with tetracycline
C. can grow on plates with tetracycline, but not with ampicillin
D. Cannot grow with any antibiotics

Answer

To solve the question, we will analyze the situation step by step:

### Step-by-Step Solution:

1. **Understanding the Plasmid**:
- The plasmid contains two antibiotic-resistance genes: one for ampicillin and one for tetracycline.

2. **Action of Restriction Enzyme**:
- A restriction enzyme is used to cut the plasmid at a specific site within the ampicillin resistance gene. This results in the inactivation of the ampicillin resistance gene because the sequence is disrupted.

3. **Preparation of Hemoglobin Gene**:
- DNA fragments containing a hemoglobin gene are also cut with the same restriction enzyme. This ensures that the hemoglobin gene has compatible ends to be inserted into the plasmid.

4. **Ligation Process**:
- The cut plasmid and the hemoglobin gene fragments are mixed together and treated with ligase. The ligase enzyme facilitates the joining of the hemoglobin gene into the plasmid where the ampicillin gene was cut.

5. **Transformation of Bacterial Cells**:
- The recombinant plasmids (plasmids containing the hemoglobin gene) are introduced into bacterial cells through a process called transformation.

6. **Selection of Clones**:
- After transformation, the bacteria are plated on media containing antibiotics (ampicillin and tetracycline) to select for those that have taken up the recombinant plasmid.
- Since the ampicillin resistance gene is disrupted, the bacteria that have taken up the recombinant plasmid will not be able to grow on ampicillin but can still grow on tetracycline.

7. **Conclusion**:
- The clones that have taken up the recombinant DNA will be able to grow on tetracycline but not on ampicillin. Therefore, the correct answer is that the clones can grow on plates with tetracycline but not on ampicillin.

### Final Answer:
The clones that have taken up the recombinant DNA are the ones that can grow on plates with tetracycline but not on ampicillin.

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