Which of the following statements does not hold true for restriction enzyme?

Options

A. It recognises a palindronic nucleotide
B. It is an endonuclease
C. It is isolated from bacteriophages
D. It produces the same kind of sticky ends in different DNA molecules

Answer

To determine which statement does not hold true for restriction enzymes, we will analyze each option provided:

1. **It recognizes palindromic nucleotides.**
- **Explanation:** This statement is true. Restriction enzymes recognize specific sequences of nucleotides that are palindromic, meaning the sequence reads the same forwards and backwards on complementary strands. For example, the sequence GAATTC is palindromic.

2. **It is endonucleases.**
- **Explanation:** This statement is also true. Restriction enzymes are a type of endonuclease, which means they cut DNA at specific sites within the molecule rather than at the ends.

3. **It is isolated from bacteriophage.**
- **Explanation:** This statement is false. Restriction enzymes are primarily isolated from bacteria, not from bacteriophages (viruses that infect bacteria). While some restriction enzymes may have been found in bacteriophages, the majority are derived from bacterial sources.

4. **It produces two same kind of ends in different DNA molecules.**
- **Explanation:** This statement is true. When restriction enzymes cut DNA, they often produce sticky or blunt ends that can be compatible with other DNA molecules cut by the same enzyme, allowing for the joining of different DNA fragments.

Based on this analysis, the statement that does not hold true for restriction enzymes is **"it is isolated from bacteriophage."**

### Summary of Steps:
1. Analyze each statement regarding restriction enzymes.
2. Confirm the truthfulness of each statement based on biological principles.
3. Identify the statement that is false.