polymerase chain reaction n an in vitro technique for rapidly synthesizing large quantities of a given DNA segment that involves separating the DNA into its two complementary strands, binding a primer to each single strand at the end of the given DNA segment where synthesis will start, using DNA polymerase to synthesize two-stranded DNA from each single strand, and repeating the process abbr. PCR
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(PCR) a type of rapid nucleic acid amplification of specific DNA or RNA sequences, allowing small quantities of short sequences to be analyzed without cloning: oligonucleotide primers are annealed to single-stranded nucleotide sequences, which are copied by polymerase; the number of copies is geometrically amplified by repeated cycles of annealing and copying.Medical dictionary. 2011.