Which of the following steps are catalysed by Taq polymerase in a PCR reaction ?

Options

A. Denaturation of template DNA
B. Annealing of primers to template DNA
C. Extension of primer and on the template DNA
D. All of the above

Explanation

### Step-by-Step Solution:

1. **Understanding PCR Process**:
- PCR (Polymerase Chain Reaction) involves several steps: denaturation, annealing, and extension. Each step has a specific function in amplifying DNA.

2. **Role of Taq Polymerase**:
- Taq polymerase is a thermostable enzyme used in PCR. Its primary role is to synthesize new DNA strands by adding nucleotides to the growing DNA chain.

3. **Identifying Steps Catalyzed by Taq Polymerase**:
- **Denaturation**: This step involves heating the reaction to separate the DNA strands. Taq polymerase does not catalyze this step.
- **Annealing**: This step allows primers to bind to the template DNA. Taq polymerase does not catalyze this step either.
- **Extension**: This is the step where Taq polymerase is active. It synthesizes the new DNA strands by adding nucleotides to the primers, effectively elongating the DNA strand.

4. **Conclusion**:
- The only step catalyzed by Taq polymerase in a PCR reaction is the **extension** of the DNA strands.

### Final Answer:
Taq polymerase catalyzes the **extension** of the DNA strands in a PCR reaction.

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