Polymerase Chain Reaction
Author: Rodney E. Shackelford, D.O., Ph.D. (see Reviewers page)
Revised: 8 October 2014, last major update January 2010
Copyright: (c) 2008-2014, PathologyOutlines.com, Inc.
● Prior to PCR technology, obtaining multiple copies of a specific DNA sequence was commonly done but often laborious
● Most protocols involved:
(a) isolating many copies of the sequence(s) desired,
(b) cloning the DNA into a viral or bacterial plasmid vector
(c) transfecting, selecting, and growing the bacteria carrying the DNA and vector, and
(d) re-isolating the desired sequence(s) from bacterial cultures by purifying and cutting the plasmids
(a) procedure could take several weeks
(b) often difficult to get pure DNA/gene sequences from the complex mixtures typically used to obtain DNA samples
Initial discovery of PCR
● Conceived in 1983 by Kary Mullis (Wikipedia), working at Cetus Corporation as a chemist
● Initial idea was to use a pair of primers to bracket the desired DNA sequence and to copy it repeatedly using DNA polymerase
● Mullis received a $10,000 bonus from Cetus for the invention; Cetus later sold the patent to Roche for $300 million; Mullis may have received additional money for testifying on behalf of Cetus in a patent lawsuit
Later PCR related work
● Cetus initially used PCR to detect the hemoglobin sickle cell point mutation
● Mullis thought of using DNA polymerase from Thermophilus aquaticus (Taq, Wikipedia), which was heat resistant; this eliminated the need to add enzyme after every cycle of thermal denaturation of the DNA, making the technique more affordable and subject to automation
● Mullis won the Nobel Prize in Chemistry in 1993 for this work
End of Molecular Pathology > Polymerase Chain Reaction > History
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