Arrange the processes that occur in PCR in sequence:

Options

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

Answer

To arrange the processes that occur in PCR (Polymerase Chain Reaction) in sequence, we can break down the steps as follows:

### Step-by-Step Solution:

1. **Denaturation**:
- The first step in PCR is denaturation, where the double-stranded DNA is heated to a high temperature (usually between 82 to 92 degrees Celsius). This heat causes the hydrogen bonds between the complementary bases to break, resulting in the separation of the two strands of DNA.

2. **Annealing**:
- After denaturation, the temperature is lowered to allow the primers to bind to the single-stranded DNA. This step is called annealing. Primers are short sequences of nucleotides that are complementary to the target DNA sequence. They attach to the 3' ends of the separated DNA strands.

3. **Extension**:
- The final step is extension, where the temperature is raised again, and a special enzyme called Taq polymerase synthesizes new DNA strands by adding deoxyribonucleotides to the primers. This results in the formation of new double-stranded DNA molecules.

### Final Sequence:
The correct sequence of processes that occur in PCR is:
1. Denaturation
2. Annealing
3. Extension