The enzyme released by restriction protection system in bacterial cells that ensures safety of self DNA is :

Options

A. DNA polymerase
B. ligase
C. methylase
D. restriction endonuclease

Answer

To solve the question regarding the enzyme released by the restriction protection system in bacterial cells that ensures the safety of self-DNA, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for an enzyme that is part of the restriction protection system in bacteria, specifically one that protects the bacterial DNA from being cleaved by restriction endonucleases.

2. **Analyzing the Options**:
- **Option 1: DNA Polymerase**: This enzyme is responsible for synthesizing new DNA strands from nucleotides. It does not play a role in protecting DNA from restriction enzymes. Therefore, this option is incorrect.
- **Option 2: Ligase**: This enzyme is involved in joining two DNA strands together by forming a chemical bond. It does not protect DNA from cleavage. Thus, this option is also incorrect.
- **Option 3: Methylase**: This enzyme adds methyl groups to DNA. In bacteria, methylation is a key part of the restriction-modification system, where it protects the bacterial DNA from being cut by its own restriction endonucleases. This option is correct.
- **Option 4: Restriction Endonuclease**: This enzyme cuts DNA at specific sequences. While it is part of the restriction system, it does not protect the DNA; instead, it cleaves it. Therefore, this option is incorrect.

3. **Conclusion**: The enzyme that ensures the safety of self-DNA in bacterial cells by methylating it is **Methylase**. Thus, the correct answer is **Option 3: Methylase**.