Arrange the steps of PCR in decreasing order of temperature.

Options

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

Answer

To arrange the steps of PCR (Polymerase Chain Reaction) in decreasing order of temperature, we first need to identify the temperatures associated with each step:

1. **Denaturation**: This step occurs at a temperature of approximately 95°C. During denaturation, the double-stranded DNA is separated into single strands.

2. **Extension (or Polymerization)**: This step occurs at around 72°C. In this phase, the DNA polymerase synthesizes new DNA strands by adding nucleotides to the separated strands.

3. **Annealing**: This step takes place at a temperature range of 50 to 60°C. During annealing, the primers bind to the single-stranded DNA templates, allowing the DNA polymerase to start synthesizing new DNA.

Now, we can arrange these steps in decreasing order of temperature:

1. **Denaturation** (95°C)
2. **Extension (Polymerization)** (72°C)
3. **Annealing** (50-60°C)

Thus, the correct order from highest to lowest temperature is:
- Denaturation (95°C)
- Extension (72°C)
- Annealing (50-60°C)

**Final Answer**: Denaturation > Extension > Annealing