realized in has function polymerase chain reaction device PCR instrument A device that is used to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. 03/21/2010: Added because it is unclear if the thermal cycler definition is intentionally broader than PCR instrument. Contacted Melanie and Trish about this. Definitions and use of alternative terms need to be made consistent. PCR instrument