Which of the following graphs best depicts the changes in one cycle of PCR ?

Options

A.
B.
C.
D.

Answer

To determine which graph best depicts the changes in one cycle of PCR (Polymerase Chain Reaction), we need to understand the three main steps of the PCR process: denaturation, annealing, and extension. Here's a step-by-step breakdown of the process:

### Step 1: Understand the PCR Process
- **Denaturation**: The double-stranded DNA is heated to around 94°C, causing it to separate into two single strands.
- **Annealing**: The temperature is lowered to around 54°C to allow primers to bind to the single-stranded DNA.
- **Extension**: The temperature is then raised to about 72°C, where DNA polymerase synthesizes new DNA strands by adding nucleotides to the primers.

### Step 2: Analyze the Graphs
- Look for a graph that shows:
- An initial increase in temperature for denaturation.
- A decrease in temperature for annealing.
- A slight increase in temperature for extension.

### Step 3: Identify the Correct Graph
- The correct graph should reflect:
- A peak at the denaturation temperature (94°C).
- A drop to the annealing temperature (54°C).
- A rise to the extension temperature (72°C) without a significant spike.

### Conclusion
Based on the description provided in the video transcript, the correct graph that depicts the changes in one cycle of PCR is **Graph A**. This graph accurately represents the temperature changes during the PCR cycle.