The discovery of the PCR method

Everyone knows the novel or has seen the film Jurassic Park in which, thanks to laboratory techniques, the blood of a dinosaur preserved in the buccal organs of a mosquito trapped in amber is extracted and so it becomes possible to reproduce the DNA of the long extinct animal. The scientists that work in Jurassic Park used the PCR method to bring to life dinosaurs that had been extinct for millenniums, from eggs produced in the present thanks to the DNA found in the mosquito! How was this possible?
Around the beginning of the Eighties in the world of biological sciences there is another powerful revolution. The setting is always a biochemistry, molecular biology or microbiology  laboratory and the main character on which we are focusing our attention is still the DNA molecule. Few inventions have revolutionised the course of molecular biology as much and as fast as PCR, the acronym for Polymerase Chain Reaction. The polymerase chain reaction of DNA is a molecular biology technique that enables the multiplication, i.e. the copying (technically the ‘amplifying’), of a specific chain of DNA. When we talk about a specific chain of DNA we mean a fragment of nucleic acid, of which the initial and final nucleotide (the series of building blocks that make up the DNA filament) sequences are known, in other words the beginning and end of the fragment. This replication process takes place normally in nature, in the cells of our body, when the DNA contained in the nucleus unwinds from its double helix conformation and its filaments are copied by the DNA polymerase enzyme. This ordinary phase of cellular reproduction is imitated in a test tube by the PCR technique. In practise, a piece of ‘complete’ DNA with a double helix is reconstructed from a strand with a single helix. The revolutionary fact is that using this laboratory technique, man can choose to take a particular part of DNA that interests him and study and utilize it in compliance with the purpose of his research, outside the cellular mechanisms that take place in a living body.
The utilization of PCR therefore enables the ‘amplification’ of a specific tract of DNA, multiplying i.e. reproducing it, billions of times in a very short time, a little over an hour, and obtaining a great number of copies.
This laboratory technique, worked out in the first half of the Eighties by the brilliant mind of Dr. Kary B. Mullis, has enabled us to better understand the genetic information contained in the DNA of each individual, with crucial consequences in wide-ranging fields, from laboratories where pure research is carried out to hospital analysis laboratories and to courtrooms. A confirmation of the importance of this achievement is the Nobel Prize for Chemistry that Kary B. Mullis received in 1993.
Before trying to understand how a PCR ‘reaction’ (this is how a procedure that takes place in a test tube is called) applied to a specific tract of DNA works, let us learn about the life and the personality of its inventor, a charming genius of our times.

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