The document discusses the polymerase chain reaction (PCR) technique. PCR is used to amplify a specific segment of DNA to produce many copies. It involves repeated cycles of heating and cooling of the DNA sample in the presence of DNA polymerase, primers, and dNTPs. Each cycle doubles the number of copies of the target DNA segment. After many cycles, millions of copies of the specific DNA segment are produced, allowing it to be analyzed. The key components needed for PCR are a DNA template, DNA polymerase, primers, dNTPs, buffer, and repeated temperature changes.