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(PCR). A method of amplifying (increasing in number) a single piece of DNA (the stuff of genes) to get enough of it to analyze physically or chemically for DNA testing. A machine is used that uses alternate cycles of high temperature (to separate DNA’s two strands) and medium temperatures (to combine each of the two single strands with free nucleic acids to make new complementary strands), doubling the amount of DNA in the machine’s soup each cycle. A few hours in the machine automatically creates millions of identical DNA molecules from just one specimen. Needless to say, it’s extremely important that you start with the right bit of DNA, so you’re not inadvertently amplifying a bit of contamination! In the film Jurassic Park, PCR was used to amplify bits of dinosaur DNA recovered from the bellies of contemporary insects, which had been trapped and preserved for millions of years inside pieces of amber. A biopsy of a single cell from an embryo after IVF can, with PCR, produce enough DNA to test it for certain genes that cause serious genetic disease. See also preimplantation genetic diagnosis
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