Restriction' in restriction enzyme refers to

Options

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

Explanation

### Step-by-Step Solution:

1. **Understanding Restriction Enzymes**:
- Restriction enzymes, also known as restriction endonucleases, are proteins that can cut DNA at specific sequences. The term "restriction" refers to their ability to restrict the growth of certain viruses, particularly bacteriophages, by cutting their DNA.

2. **Cleaving of Phosphodiester Bonds**:
- One of the primary functions of restriction enzymes is to cleave the phosphodiester bonds in the DNA backbone. This action breaks the DNA strand, which is essential for various molecular biology applications, such as cloning and DNA analysis.

3. **Cutting DNA at Specific Positions**:
- Restriction enzymes recognize specific sequences in the DNA, known as restriction sites, and cut the DNA at these precise locations. This specificity is crucial for genetic engineering, as it allows scientists to target and manipulate specific genes.

4. **Prevention of Bacteriophage Multiplication**:
- In bacteria, restriction enzymes serve a protective role by recognizing and cutting the DNA of invading bacteriophages (viruses that infect bacteria). By cutting the viral DNA, these enzymes prevent the bacteriophage from replicating within the bacterial cell.

5. **Conclusion**:
- The term "restriction" in restriction enzymes encompasses all the functions mentioned: cleaving phosphodiester bonds, cutting DNA at specific positions, and preventing the multiplication of bacteriophages. Therefore, the correct answer to the question is option D: all of the above.