PCR Thermal Cycling – AP Biology

The Three Phases

1. Denaturation (95°C): Heat breaks the hydrogen bonds, unzipping the double stranded DNA.

2. Annealing (55°C): Cooling allows designed synthetic primers to bind to target sequences.

3. Extension (72°C): Taq Polymerase synthesizes new DNA strands robustly at its optimal temp.

Exponential Growth

Each thermal cycle doubles the amount of target DNA.

\( N_n = N_0 \times 2^n \)

Taq Polymerase

Isolated from Thermus aquaticus (hot springs). It survives the 95°C denaturation phase without denaturing itself!