At which temperature a DNA molecule is denatured by heat in PCR

Options

A. `70^(@)-80^(@)C`
B. `90^(@) - 95^(@)C`
C. `42^(@)C`
D. `50^(@) - 65^(@)C`

Answer

To determine the temperature at which a DNA molecule is denatured by heat in PCR (Polymerase Chain Reaction), we can follow these steps:

### Step-by-Step Solution:

1. **Understand PCR**:
- PCR stands for Polymerase Chain Reaction, a technique used to amplify DNA, creating millions of copies of a specific DNA sequence.

2. **Identify the Steps of PCR**:
- The PCR process consists of three main steps:
- **Denaturation**: The double-stranded DNA is heated to separate it into two single strands.
- **Annealing**: Primers bind to the single-stranded DNA.
- **Extension**: DNA polymerase synthesizes new DNA strands.

3. **Focus on the Denaturation Step**:
- The denaturation step is crucial as it involves breaking the hydrogen bonds between the DNA strands, resulting in single-stranded DNA.

4. **Determine the Temperature for Denaturation**:
- Denaturation occurs at high temperatures. The typical temperature range for denaturation in PCR is between 90°C to 95°C.

5. **Select the Correct Option**:
- Given the options:
- 70-80°C
- **90-95°C** (Correct Answer)
- 42°C
- 50-65°C
- The correct answer is **90-95°C**.

### Final Answer:
The DNA molecule is denatured by heat in PCR at a temperature of **90-95°C**.

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