John M. S. Bartlett.pdf - Bio-Nica.info

History of PCR 5
Fig. 1. Results of a PubMed search for articles containing the phrase “Polymerase Chain
Reaction.” Graph shows number of articles listed in each year.
However, even with this improvement, the PCR technique was laborious and slow,
requiring manual transfer between water baths at different temperatures. The first
thermocycling machine, “Mr Cycle,” which replicated the temperature changes required
for the PCR reaction without the need for manual transfer, was developed by Cetus
to facilitate the addition of fresh thermolabile polymerases. After the purification of
Taq polymerase, Cetus and Perkin–Elmer introduced the closed DNA thermal cyclers
that are widely used today (7).
That PCR has become one of the most widely used tools in molecular biology is
clear from Fig. 1. What is not clear from this simplistic analysis of the literature is the
huge range of questions that PCR is being used to answer. Another scientist at Cetus,
Stephen Scharf, is quoted as stating that
…the truly astonishing thing about PCR is precisely that it wasn’t designed to solve
a problem; once it existed, problems began to emerge to which it could be applied. One
of PCR’s distinctive characteristics is unquestionably its extraordinary versatility. That
versatility is more than its ‘applicability’ to many different situations. PCR is a tool that
has the power to create new situations for its use and those required to use it.
More than 3% of all PubMed citations now refer to PCR (Fig. 2). Techniques have
been developed in areas as diverse as criminal forensic investigations, food science,
ecological field studies, and diagnostic medicine. Just as diverse are the range of
adaptations and variations on the original theme, some of which are exemplified in
this volume. The enormous advances made in our understanding of the human genome
(and that of many other species), would not have been possible, where it not for the
remarkable simple and yet exquisitely adaptable technique which is PCR.