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The history of the polymerase chain reaction (PCR) has variously been described as a classic "Eureka!" moment, [1] or as an example of cooperative teamwork between disparate researchers. [2] Following is a list of events before, during, and after its development:
- one would hope to obtain two structures, each containing the full length of the template strand appropriately complexed with the primer. DNA polymerase will be added to complete the process of repair replication. Two molecules of the original duplex should result. The whole cycle could be repeated, there being added every time a fresh dose of the enzyme.
By 1980 all of the components needed to perform PCR amplification were known to the scientific community. The use of DNA polymerase to extend oligonucleotide primers was a common procedure in DNA sequencing and the production of cDNA for cloning and expression. The use of DNA polymerase for nick translation was the most common method used to label DNA probes for Southern blotting.
In December 1985, a joint venture between Cetus and Perkin-Elmer was established to develop instruments and reagents for PCR. Complex thermal cyclers were constructed to perform the Klenow-based amplifications; however, they were never marketed. Simpler machines for Taq-based PCR were developed, and on November 19, 1987, a press release announced the commercial availability of the "PCR-1000 Thermal Cycler" and "AmpliTaq DNA Polymerase".
In the spring of 1985, John Sninsky at Cetus began to use PCR for the difficult task of measuring the amount of HIV circulating in blood. A viable test was announced on April 11, 1986, and published in May 1987. [26] Donated blood could then be screened for the virus, and the effect of antiviral drugs directly monitored.
In 1985, Norm Arnheim, also a member of the development team, concluded his sabbatical at Cetus and assumed an academic position at University of Southern California. He began to investigate the use of PCR to amplify samples containing just a single copy of the target sequence. By 1989 his lab developed multiplex-PCR on single sperm to directly analyze the products of meiotic recombination. [27] These single-copy amplifications, which had first been run during the characterization of Taq polymerase, [24] became vital to the study of ancient DNA, as well as the genetic typing of preimplanted embryos.
In 1986, Edward Blake, a forensics scientist working in the Cetus building, collaborated with Henry Erlich, a researcher at Cetus, to apply PCR to the analysis of criminal evidence. A panel of DNA samples from old cases was collected and coded and was analyzed blind by Saiki using the HLA DQα assay. When the code was broken, all of the evidence and perpetrators matched. Blake and Erlich's group used the technique almost immediately in Pennsylvania v. Pestinikas, [28] the first use of PCR in a criminal case. This DQα test was developed by Cetus as one of their "Ampli-Type" kits and became part of early protocols for the testing of forensic evidence, such as in the O. J. Simpson murder case.
By 1989, Alec Jeffreys, who had earlier developed and applied the first DNA Fingerprinting tests, used PCR to increase their sensitivity. [29] With further modification, the amplification of highly polymorphic Variable number tandem repeat (VNTR) loci became the standard protocol for National DNA Databases such as Combined DNA Index System (CODIS).
In 1987, Russ Higuchi succeeded in amplifying DNA from a human hair. [30] This work expanded to develop methods for the amplification of DNA from highly degraded samples, such as from ancient DNA and in forensic evidence.