Polymerase chain reaction (PCR) is a molecular biology technique used to amplify a specific segment of nucleic acid—typically DNA—from a sample. The process involves cycling through temperatures that denature the double-stranded DNA, allowing primers to bind to the target regions, and then allowing a heat-stable DNA polymerase enzyme to synthesize complementary DNA strands. Because the DNA fragments are exponentially multiplied in each cycle, minute amounts of target genetic material can be detected and studied in a highly sensitive manner. This technique is foundational in diagnostic testing, genetic research, and forensic science for analyzing genetic identity.