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 need to identify the temperature associated with each of the three main steps: denaturation, annealing, and extension.

1. **Denaturation**: This is the first step in the PCR process where the double-stranded DNA is heated to separate it into two single strands. This occurs at a high temperature of approximately **98°C**.

2. **Extension**: In this step, the DNA polymerase enzyme synthesizes new DNA strands by adding nucleotides to the primers. This process typically occurs at a temperature of about **72°C**.

3. **Annealing**: This step involves the binding of primers to the single-stranded DNA template. The temperature for this step is lower, usually around **50-60°C**.

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

1. **Denaturation** (98°C)
2. **Extension** (72°C)
3. **Annealing** (50-60°C)

Thus, the correct order is:
- Denaturation
- Extension
- Annealing