I See the Light! And I See It Again and Again!

In 1983, Kary Mullis at Cetus conceptualized the most important of biotechnological reactions—the polymerase chain reaction (PCR) (1). The idea, for which Mullis was awarded the 1993 Nobel Prize in chemistry, was as simple as it was brilliant. Given the natural ability of polymerases to copy nucleic acids in the presence of short complementary oligonucleotides it should be possible to perform the reaction in cycles to produce large numbers of copies of virtually any DNA sequence. In the beginning, fresh polymerase had to be added at each cycle, because it was irreversibly denatured by the heating. In 1985, Susanne Stoffel and David Gelfand successfully isolated DNA polymerase from Thermus aquaticus (i.e., Taq ), and Randy Saiki showed that it could be used to automate the process (2). Heating to 95 °C separated the strands of the nucleic acid template, a temperature between 50 °C and 60 °C allowed primer oligonucleotides to hybridize with template, and raising the temperature to 72 °C activated the heat-stable Taq polymerase to extend the primers to generate a copy of the template molecule. With the PCR, virtually any DNA molecule could be amplified to large amounts from a single copy. The technique rapidly became important in biological research, for …