In 1963 the two enzymes responsible for restricting the growth of bacteriophage in E.coli were isolated and one of these is used

Options

A. to remove methyl groups to DNA
B. to cut DNA
C. to join DNA fragments
D. to add ethyl enzyme is

Answer

**Step-by-Step Solution:**

1. **Understanding the Context**: In 1963, two enzymes were isolated that restrict the growth of bacteriophage in E. coli. These enzymes are crucial for understanding how bacteria protect themselves from viral infections.

2. **Identifying the Enzymes**: The two enzymes mentioned are:
- **Methylase**: This enzyme adds a methyl group to specific DNA sequences, which helps protect the bacterial DNA from being cut by restriction enzymes.
- **Restriction Endonuclease**: This enzyme recognizes specific palindromic sequences in DNA and cuts the DNA at these sites.

3. **Analyzing the Options**:
- **Option 1: Remove methyl group from DNA**: This is incorrect because methylase adds methyl groups, not removes them.
- **Option 2: Cut DNA**: This is correct as restriction endonucleases are specifically responsible for cutting DNA at specific sequences.
- **Option 3: Join DNA fragments**: This is incorrect because joining DNA fragments is the function of ligase enzymes, not restriction endonucleases.
- **Option 4: Add ethylene enzyme**: This is incorrect as neither methylase nor restriction endonucleases add ethylene groups.

4. **Conclusion**: Based on the analysis, the correct answer is that one of the enzymes is used to **cut DNA**.

**Final Answer**: The enzyme responsible for restricting the growth of bacteriophage in E. coli is used to **cut DNA**.

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