Chemical knives of DNA are :

Options

A. endonucleases
B. ligases
C. transcriptases
D. polymerases

Answer

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks about the "chemical knives of DNA," which refers to enzymes that cut DNA.

2. **Understand the Options**: The options provided are:
- 1. Andronucleases
- 2. Ligases
- 3. Transcriptases
- 4. Polymerases

3. **Analyze Each Option**:
- **Andronucleases**: These are enzymes that cut DNA at specific sites. They are often referred to as restriction enzymes or restriction endonucleases, which are indeed known as "chemical knives" because they cleave the DNA molecule.
- **Ligases**: These enzymes join DNA fragments together. They do not cut DNA, so they cannot be considered chemical knives.
- **Transcriptases**: These enzymes are involved in the transcription process, converting DNA into RNA. They do not cut DNA, so they are not chemical knives.
- **Polymerases**: These enzymes synthesize DNA or RNA from nucleotides. They are also not involved in cutting DNA.

4. **Conclusion**: Based on the analysis, the only enzyme that fits the description of "chemical knives" is **Andronucleases** (specifically, restriction endonucleases).

5. **Final Answer**: The correct answer is **1. Andronucleases**.

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