Polymerase Chain Reaction (PCR) The elegant technique of PCR, by which fragments of DNA can be made to replicate very rapidly, is illustrated.

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Polymerase chain reaction (PCR), is a common method of creating copies of specific fragments of DNA. PCR rapidly amplifies a single DNA molecule into many billions of molecules.

In one application of the technology, small samples of DNA, such as those found in a strand of hair at a crime scene, can produce sufficient copies to carry out forensic tests.