Bacteria possessing restriction endonucleases remain

Options

A. Affected by bacteriophages
B. Resistant to bacteriophages
C. Resistant to drugs
D. Resistant to heat

Answer

### Step-by-Step Solution:

1. **Understanding Restriction Endonucleases**:
- Restriction endonucleases are enzymes found in bacteria that cut DNA at specific sequences. They serve as a defense mechanism against foreign DNA, such as that from bacteriophages (viruses that infect bacteria).

2. **Function of Restriction Endonucleases**:
- When a bacteriophage infects a bacterium, it injects its DNA into the bacterial cell. The restriction endonucleases recognize and cleave this foreign DNA, preventing the bacteriophage from replicating and ultimately leading to its death.

3. **Analyzing the Options**:
- The question provides four options regarding the state of bacteria possessing restriction endonucleases:
- A) Affected by the bacteriophages
- B) Resistant to bacteriophages
- C) Resistant to drugs
- D) Resistant to heat

4. **Evaluating Each Option**:
- **Option A (Affected by the bacteriophages)**: This is incorrect because the presence of restriction endonucleases provides a defense against bacteriophages.
- **Option B (Resistant to bacteriophages)**: This is correct. The restriction endonucleases allow bacteria to resist infection by bacteriophages by cutting their DNA.
- **Option C (Resistant to drugs)**: This is not relevant to the function of restriction endonucleases.
- **Option D (Resistant to heat)**: This is also not related to the function of restriction endonucleases.

5. **Conclusion**:
- The correct answer is **B) Resistant to bacteriophages**. Bacteria with restriction endonucleases can effectively defend themselves against bacteriophage attacks.