Restriction' in restriction enzyme refers to

Options

A. cleaving of phosphodiester bond in DNA by the enzyme
B. cutting of DNA at specific position only
C. prevention of the multiplication of bacteriophage in bacteria
D. all of the above

Answer

### Step-by-Step Solution:

1. **Understanding Restriction Enzymes**:
- Restriction enzymes, also known as restriction endonucleases, are proteins produced by bacteria that can cut DNA at specific sequences. They serve as a defense mechanism against invading viruses (bacteriophages).

2. **Definition of 'Restriction'**:
- The term 'restriction' in restriction enzymes refers to the ability of these enzymes to restrict or limit the growth of bacteriophages by cleaving foreign DNA. This is a protective mechanism for the bacteria.

3. **Mechanism of Action**:
- When a bacteriophage infects a bacterium, the restriction enzyme recognizes specific sequences in the viral DNA and cuts it. This prevents the bacteriophage from replicating and causing harm to the bacterial cell.

4. **Options Analysis**:
- Option A: "Cleaving of phosphodiester bond in DNA by the enzyme" - This is a general function of nucleases but does not capture the essence of 'restriction.'
- Option B: "Cutting of DNA at specific position only" - This describes the specificity of restriction enzymes but does not encompass the broader meaning of 'restriction.'
- Option C: "Prevention of the multiplication of bacteriophage in bacteria" - This accurately describes the role of restriction enzymes in bacterial defense.
- Option D: "All of the above" - Since not all options are correct, this cannot be the answer.

5. **Conclusion**:
- The correct answer is **Option C: Prevention of the multiplication of bacteriophage in bacteria**. This highlights the primary function of restriction enzymes in the context of bacterial immunity.