Also called "molecular photocopying it is a fast and inexpensive technique used to "amplify" - copy - small segments of DNA. Because significant amounts of a sample of DNA are necessary for molecular and genetic analyses, studies of isolated pieces of DNA are nearly impossible without PCR amplification.
B. Mullis, was awarded the Nobel Prize for Chemistry in 1993 for this.
What is the Theory of PCR?
How does PCR work?
1. A sample is first heated so the DNA denatures, (breaks down) or separates into two pieces of single-stranded DNA.
2. An enzyme called "Taq polymerase" synthesizes - builds - two new strands of DNA, using the original strands as templates.
3. This process results in the duplication of the original DNA, with each of the new molecules containing one old and one new strand of DNA. Then each of these strands can be used to create two new copies, and so on, and so on.
4. The cycle of denaturing and synthesizing new DNA is repeated as many leading to more than one billion exact copies of the original DNA segment.
5. The entire cycling process of PCR is automated and can be completed in 2 hours
6. It is directed by a machine called a thermocycler, which is programmed to alter the temperature of the reaction every few minutes to allow DNA denaturing and synthesis.