The correct order of steps in Polymerase Chain Reaction (PCR) is

Options

A. Annealing, Extension, Denaturation
B. Denaturation, Extension, Annealing
C. Extension, Denaturation, Annealing
D. Denaturation, Annealing, Extension

Answer

**Step-by-Step Solution:**

1. **Understanding PCR**: Polymerase Chain Reaction (PCR) is a technique used to amplify specific DNA sequences. It was developed by Kary Mullis and involves a series of temperature changes.

2. **Step 1 - Denaturation**: The first step in PCR is denaturation. This involves heating the DNA to about 90-91 degrees Celsius, which breaks the hydrogen bonds between the two strands of DNA, causing them to separate. This results in two single strands that can serve as templates for replication.

3. **Step 2 - Annealing**: After denaturation, the temperature is lowered to about 50-55 degrees Celsius. This allows primers to bind (anneal) to the single-stranded DNA templates. Primers are short sequences of nucleotides that are complementary to the target DNA sequence.

4. **Step 3 - Extension**: The final step is extension, where the temperature is raised to approximately 72 degrees Celsius. In this step, the DNA polymerase enzyme adds nucleotides to the growing DNA strand, synthesizing a new strand complementary to the template strand.

5. **Correct Order**: The correct order of steps in PCR is:
- Denaturation
- Annealing
- Extension

**Conclusion**: Therefore, the correct sequence of steps in Polymerase Chain Reaction (PCR) is denaturation, annealing, and extension.

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