A PCR (polymerase chain reaction) test is a lab technique that amplifies (creates more copies) of genetic material (DNA). Healthcare providers can use PCR to test for infectious diseases, to look for genetic changes in tumors or to diagnose genetic diseases.
PCR is fundamental to many of the procedures used in genetic testing, research, including analysis of ancient samples of DNA and identification of infectious agents. Using PCR, copies of very small amounts of DNA sequences are exponentially amplified in a series of cycles of temperature changes.
To amplify a segment of DNA using PCR, the sample is first heated so the DNA denatures, or separates into two pieces of single-stranded DNA. Next, an enzyme called "Taq polymerase" synthesizes - builds - two new strands of DNA, using the original strands as templates.