Quantitative and reverse transcription PCR

Polymerase chain reaction (PCR) is a method to generate copies of specific DNA sequences in the lab. Similar to DNA replication in the cell, double-stranded DNA is separated and each strand serves as the template for a complementary strand. In each round of replication the quantity of DNA doubles. Unlike DNA replication in the cell, the replication process starts with the binding of a short complementary sequence called a primer to the target DNA.

Quantitative PCR (qPCR) is a variation of PCR where the initial amount of DNA in the sample is determined by measuring the rate of replication. Through the use of fluorescent probes or dyes that only fluoresce when bound to double-stranded DNA, replication can be measured in real-time. By using primers specific for a certain pathogen, the generation of DNA and therefore fluorescence is indicative of the presence of DNA from this pathogen.