PCR

"PCR" stands for polymerase chain reaction. Using this technique, short stretches (some hundred nucleotides) of DNA molecules are multiplied several billion fold.

The method relies on the repeated (30 to 40 fold) duplication of a given stretch of DNA, using heat stable enzymes of certain archeae. The DNA-stretch in question is determined by accordingly designed primers (red arrows) for the multiplying enzyme. The PCR is used for the production of defined DNA molecules starting from minimal amounts of sample material.