PCR uses DNA primers. PCR (polymerase chain reaction) is a laboratory technique that’s used to rapidly amplify or make many copies of a specific DNA segment in vitro or in a test tube.  This requires the use of short synthetic DNA fragments called DNA primers. DNA primers are used to select a segment of the genome to be amplified. The selected segment is then amplified after going through multiple cycles of DNA synthesis. RNA primers are used in replication in vivo or in the organism itself.