Polymerase Chain Reaction Learning Path

Purpose and exponential DNA amplification

Polymerase chain reaction (PCR) is a laboratory technique used to rapidly make many copies of a specific DNA sequence so that small starting amounts can be studied. It relies on repeated temperature changes (thermal cycling) to drive DNA melting (denaturation), primer binding (annealing), and DNA synthesis (extension) by a thermostable DNA polymerase. Two primers define the target region, and the newly synthesized DNA becomes template for the next cycle. The key feature is exponential amplification: ideally, the amount of target DNA doubles each cycle. After n cycles, the expected number of copies is approximately 2^n, so even a single DNA template can be amplified to very large quantities (e.g., 2^30 ≈ 1.07 billion copies). In real reactions, amplification proceeds through stages—an initial exponential phase, followed by a leveling-off stage as reagents and enzyme activity become limiting, and finally a plateau when substrates are exhausted and product no longer increases.

0/2 modes complete

Thermal cycling concept and temperature-dependent reactions

0/2 modes complete