Polymerase Chain Reaction (PCR) is a method of creating multiple copies (i.e. amplifying) of a particular segment of DNA. This is a useful component in DNA cloning since it can provide multiple copies of the experimental sequence that can be used for further tests.
In PCR, a thermal cycler is used to shift through different temperature levels. These lead us to three major steps: denaturation, annealing, and extension. The PCR starts with the system reaching equilibrium then adjusted to denature, followed by the annealing step, and ends with the extension step.