Which of the following shows the correct sequence of processes with respect to the PCR ?

Options

A. Extension , denaturation , annealing
B. Denaturation , annealing , extension
C. Denaturation , extension , annealing
D. Annealing , extension , denaturation

Answer

To solve the question regarding the correct sequence of processes in the Polymerase Chain Reaction (PCR), let's break down the steps involved in PCR:

### Step-by-Step Solution:

1. **Denaturation**:
- The first step in PCR is denaturation. In this step, the double-stranded DNA is heated to a high temperature (typically around 94-98°C). This heat causes the hydrogen bonds between the base pairs to break, resulting in the separation of the two strands of DNA.

2. **Annealing**:
- After denaturation, the temperature is lowered (usually to about 50-65°C) in the annealing step. This allows short DNA primers to bind or anneal to the complementary sequences on the single-stranded DNA templates. The primers are essential for initiating the synthesis of the new DNA strands.

3. **Extension (or Elongation)**:
- The final step is extension (also referred to as elongation). The temperature is raised again (to around 72°C), which is optimal for the enzyme Taq polymerase to synthesize new DNA strands. Taq polymerase adds nucleotides to the 3' end of the primers, thereby extending the new DNA strands.

### Conclusion:
The correct sequence of processes in PCR is:
- **Denaturation → Annealing → Extension**

### Answer:
The correct option is **Denaturation, Annealing, Extension**.