Which one of the following is not required in PCR?

Options

A. Oligonucleotide primers
B. Helicase enzyme
C. DNA template
D. Taq polymerase

Answer

### Step-by-Step Solution:

1. **Understand PCR**: PCR stands for Polymerase Chain Reaction, a technique used to amplify DNA. It requires specific components to function properly.

2. **Identify Required Components**: The essential components for PCR include:
- **DNA Template**: The DNA that you want to amplify.
- **Oligonucleotide Primers**: Short sequences of nucleotides that provide a starting point for DNA synthesis. You need both forward and reverse primers.
- **dNTPs (deoxynucleotide triphosphates)**: The building blocks of DNA, which include adenine (A), cytosine (C), guanine (G), and thymine (T).
- **Taq Polymerase**: A heat-stable enzyme that synthesizes new DNA strands.
- **Thermocycler**: A machine that changes temperatures to facilitate the different steps of PCR (denaturation, annealing, and extension).
- **Magnesium Ions**: Often required as a cofactor for Taq polymerase to function effectively.

3. **Analyze the Options**: The question asks which component is NOT required for PCR. The options typically include:
- Oligonucleotide primer
- Helicase enzyme
- DNA template
- Taq polymerase

4. **Determine the Incorrect Component**:
- **Oligonucleotide Primer**: Required for PCR.
- **Helicase Enzyme**: Not required for PCR because the DNA strands are separated by the denaturation step, which is achieved through heating, not by helicase.
- **DNA Template**: Required for PCR.
- **Taq Polymerase**: Required for PCR.

5. **Conclusion**: The component that is NOT required in PCR is the **Helicase enzyme**.

### Final Answer:
Helicase enzyme is not required in PCR.