Polymerase Chain Reaction (PCR) Applications

Reverse Transcriptase PCR (RT-PCR)

RT-PCR, or reverse transcriptase PCR, is a variation of the standard PCR technique that involves the amplification of specific mRNA obtained from very small samples. It eliminates the need for the tedious mRNA purification process required for conventional cloning techniques. With RT-PCR, reverse transcriptase and an RNA sample are used in addition to the standard PCR reagents. The reaction mixture is heated to 37 ˚C, which allows for the production of complementary cDNA copy from the RNA sample by reverse transcriptase. This cDNA then anneals to one of the primers leading to first strand synthesis. Standard PCR follows from here in which dsDNA is ultimately generated. RT-PCR is frequently combined with real time PCR (qPCR), which is widely used for the quantification of transcript levels in cells and tissues.

Hot Start PCR

Hot Start PCR is a technology that inhibits hot start Taq polymerase or the incorporation of modified dNTPs during reaction set up until a heat activation step occurs. Various methods are available to arrest hot start polymerase activity and include, chemical modification, antibody-mediated, and aptamer-mediated methods. 

Endpoint PCR for Long and Accurate Target Amplification

Endpoint PCR is often used to detect the presence of targets and relative abundance at the completion of the reaction. The limited length of sequences produced during standard PCR, approximately 5 kb, is in part overcome with the incorporation of additional factors that provide “proofreading” activity. Long and accurate (LA) PCR incorporates the use of a second thermostable polymerase with 3′→5′ exonuclease to repair terminal nucleotide misincorporations, resulting in significantly increased fidelity and the ability to amplify DNA targets up to 40 kb in length.