Tuesday, May 16, 2006
Imagination and Scientific Method
Initially, PCR used an E. coli DNA polymerase I derivative called Klenow Fragment. Enzyme had to be added every cycle because the enzyme was destroyed by the heat necessary to unwind the DNA molecules so that the primers could anneal to them to create more copies. Once they used a heat stable version of Klenow fragment from a hyperthermophilic bacterium, was the technique easy to use and economical. The imagination lies in the use of repeating cycles of denaturation (heating) of the DNA template(s), of renaturation (cooling) to allow annealing of excess primers to the DNA strands, and of a heat stable DNA polymerase to generate new copies of DNA, thereby allowing one amplify any sequence of DNA one wants. The bacteria and enzymology were known in the late 1960s. The piece of technology that held everything up was the oligonucleotide polymerization chemistry . That technology came along in the late 1970s-early 1980s. The heat stable DNA polymerase was a just an elegant, key refinement to the technique. PCR was thought up in 1983, but, it didn't become ubiquitous in the biochemical or molecular biological labs until the late 1980s. Now, everyone uses the technique. No scientific methodology was involved, just pure imagination and creativity for the initial idea.
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