Kary Mullis won the 1993 Nobel Prize in Chemistry for inventing the polymerase chain reaction, or PCR.
PCR is a laboratory method that rapidly makes millions of copies of a selected DNA segment. Mullis conceived the basic idea in 1983 while working at Cetus Corporation, and the method became practical after the use of heat-stable DNA polymerase from Thermus aquaticus.
The enzyme is commonly called Taq polymerase. PCR uses repeated cycles of heating and cooling to separate DNA strands, copy them, and amplify the target sequence. It transformed medical diagnosis, genetic research, forensic science, and infectious-disease testing.
Mullis shared the 1993 Chemistry Nobel with Michael Smith, who was honored for developing site-directed mutagenesis. The prize recognized PCR itself, not the discovery of DNA or the invention of DNA sequencing.