3'-5' exonucleolytic degradation of DNA is performed by which enzyme ?

Options

A. a.DNA polymerase
B. b.Alkaline phosphatase
C. c.DNA ligase
D. d.RNA polymerase

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which enzyme is responsible for the 3'-5' exonucleolytic degradation of DNA. This process involves the breakdown of DNA from the 3' end to the 5' end.

2. **Identifying the Enzymes**: The options provided are:
- DNA polymerase
- Alkaline phosphatase
- DNA ligase
- RNA polymerase

3. **Analyzing Each Option**:
- **DNA Polymerase**: This enzyme is primarily involved in DNA replication and has exonuclease activity that allows it to degrade DNA in the 3'-5' direction. It hydrolyzes phosphodiester bonds during the synthesis of DNA.
- **Alkaline Phosphatase**: This enzyme is involved in the removal of phosphate groups from molecules, primarily proteins, and does not play a role in DNA degradation.
- **DNA Ligase**: This enzyme is responsible for joining DNA fragments together by forming phosphodiester bonds, thus maintaining genomic integrity. It does not degrade DNA.
- **RNA Polymerase**: This enzyme synthesizes RNA from a DNA template during transcription and does not participate in DNA degradation.

4. **Conclusion**: Based on the analysis, DNA polymerase is the enzyme that performs 3'-5' exonucleolytic degradation of DNA.

5. **Final Answer**: The enzyme responsible for 3'-5' exonucleolytic degradation of DNA is **DNA polymerase**.

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