In the polymerase chain reaction, the optimum temperature for the polymerization step is

Options

A. `72^@C`
B. `50^@C`
C. `90^@C`
D. `45^@C`

Answer

To solve the question regarding the optimum temperature for the polymerization step in the polymerase chain reaction (PCR), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Process of PCR**:
- PCR is a technique used to amplify DNA. It involves three main steps: denaturation, annealing, and extension (or polymerization).

2. **Identify the Steps of PCR**:
- **Denaturation**: This is the first step where the double-stranded DNA is heated to separate it into two single strands. This typically occurs at around 94°C.
- **Annealing**: In this second step, primers bind to the single-stranded DNA. The temperature for this step usually ranges from 40°C to 65°C, depending on the melting temperature of the primers used.
- **Extension (Polymerization)**: This is the third step where the DNA polymerase enzyme synthesizes new DNA strands by adding nucleotides.

3. **Determine the Optimum Temperature for Extension**:
- The enzyme commonly used in PCR is Taq DNA polymerase, which operates optimally at around 72°C. This is the temperature at which the polymerization step occurs.

4. **Select the Correct Answer**:
- Given the options:
- 72°C
- 50°C
- 90°C
- 45°C
- The optimum temperature for the polymerization step is **72°C**.

### Conclusion:
The optimum temperature for the polymerization step in the polymerase chain reaction (PCR) is **72 degrees Celsius**.

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