what is the purpose of PCR
The polymerase chain reaction (PCR) is a technology in molecular biology used to amplify a single copy or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. If the genomic DNA sequence of a gene is known, RT-PCR can be used to map the location of exons and introns in the gene. 2  The 5' end of a gene (corresponding to the transcription start site) is typically identified by RACE-PCR (Rapid Amplification of cDNA Ends).