What is PCR?

PCR stands for Polymerase Chain Reaction. It is an experimental technique used to amplify a sample of DNA. It requires a number of things: a DNA sample, oligonucleotide primers for either side of the desired sequence, a heat-resistant DNA polymerase, a supply of nucleotides, correct buffer, and a thermocycler. These are mixed in the thermocycler and heated to ~94 degrees celsius so the dsDNA sample denatures into two single stranded molecules. It is then cooled to ~54 degrees celsius to allow your complementary oligonucleotide primers to anneal to the strands. The temperature is raised to ~72 degrees celsius where the DNA polymerase binds and adds the first nucleotide to the 3' hydroxyl on the primer and continues adding nucleotides until it completes the strand. There is now 2 strands of your dsDNA sequence. This is repeated for 30-35 cycles to leave you with a large amount of the DNA sample from the start.