Recognized as one of the most important scientific advances of the 20th century,1 polymerase chain reaction (PCR) is a quick, easy way to create unlimited copies of DNA from just one original strand. Millions of copies of a section of DNA are made in just a few hours. The copied DNA can then be used reliably in a wide variety of tests to diagnose or monitor diseases, or for basic molecular biology research.
PCR was awarded the 1993 Nobel Prize in Chemistry.
The evolution and revolution of PCR
In 1983, Kary Mullis, PhD, a scientist at the Cetus Corporation, conceived of PCR as a method to copy DNA and synthesise large amounts of a specific target DNA. Over the next two years, a team of Cetus scientists that recognised the potential impact PCR could have on molecular biology, researched, refined and made the theoretical process a reality.
The team presented for the first time in 1985 at the American Society for Human Genetics annual meeting.2 Later that year, Science, a journal of the American Association for the Advancement of Science3 , reported the results in the first-ever publication of the process.
Two significant advances have enabled PCR to become the technology it is today – Taq polymerase and the thermal cycler.
In 1986, Cetus scientists isolated the Taq polymerase from Thermus aquaticus, a bacterium found in hot springs. Because Taq could withstand high temperatures, it removed the need for human intervention during the reaction,4 streamlining and shortening the process. Without a heat-resistant enzyme like Taq polymerase, PCR could not be used on a large scale as the process would have been too cumbersome.
Prior to Taq, DNA polymerase from E. coli, an enzyme that could not withstand rapid heating and cooling, was used in the second step of PCR. Using E. Coli, the polymerase was manually replaced at each step of the reaction as it degraded from the heat5 .
In 1987, PerkinElmer, another US-based biotech company, launched a thermal cycler, an instrument that is programmed to regulate the temperature of a reaction, heating or cooling the samples as needed. Once again, this advance minimised human interaction in the reaction, leading to an elegant, efficient and streamlined process.
The birth of Roche Molecular Diagnostics
In 1991, Roche bought the rights to PCR from Cetus and invested in refining the science for use in molecular diagnostics to detect diseases. Roche Molecular Diagnostics has not only defined and refined PCR, but it has remained the clear leader and trailblazer of this technology.