PCR and DNA Amplification Explained

Polymerase Chain Reaction (PCR) is a technique that amplifies (copies) a specific DNA segment, producing millions to billions of copies from a single starting molecule.

PCR has three main steps per cycle: 1) Denaturation (95°C) — DNA strands separate. 2) Annealing (50-65°C) — primers bind to target sequences. 3) Extension (72°C) — Taq polymerase builds new strands.

Theoretically, each cycle doubles the DNA. After n cycles: copies = initial × 2ⁿ. For 30 cycles: 2³⁰ ≈ 1 billion copies. Real PCR efficiency is 80-100% due to reagent depletion.

Key components: Template DNA, Primers (forward & reverse), Taq polymerase (heat-stable), dNTPs (building blocks), Buffer, Mg²⁺ (cofactor).

Melting temperature (Tm) of primers should be 55-65°C, and the annealing temperature is typically set 3-5°C below Tm. GC content should be 40-60%.

Use our PCR Amplification Calculator and Melting Temperature (Tm) Calculator in the Molecular Biology category to plan your experiments.