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  • What is Fidelity?

    Return to High-Fidelity PCR

    New England Biolabs has been involved in the discovery and development of high fidelity polymerases for many years (Table 1). Beginning with the discovery of VentR® DNA Polymerase from Thermococcus litoralis in 1990 (1,2), NEB researchers have identified and engineered several high fidelity polymerases – all with differing processivities, speeds and degrees of accuracy.

    New England Biolabs' High-Fidelity DNA Polymerase History

    1990-91 VentR® DNA Polymerase M0254
    1992 VentR® (exo-) DNA Polymerase
    Deep VentR™ DNA Polymerase
    1993-1994 Deep VentR™ (exo-) DNA Polymerase M0259
    1995 9°Nm™ DNA Polymerase M0260
    2007-2008 Phusion® High-Fidelity DNA Polymerase M0530
    2011 Phusion® Hot Start Flex DNA Polymerase M0535
    2012 Q5® High-Fidelity DNA Polymerase
    Q5® Hot Start High-Fidelity DNA Polymerase

    The fidelity of a DNA polymerase refers to its ability to accurately replicate a template. A critical aspect of this is the ability of the DNA polymerase to read a template strand, select the appropriate nucleoside triphosphate and insert the correct nucleotide at the 3' primer terminus, such that canonical Watson-Crick base pairing is maintained. The rate of misincorporation (incorporating the incorrect nucleotide) is known as the polymerase's "error rate". In addition to effective discrimination for correct over incorrect nucleotide incorporation, some DNA polymerases possess a 3'→5' exonuclease activity. This activity, also termed "proofreading", is used to excise incorrectly incorporated mononucleotides that are then replaced with the correct nucleotide. High-fidelity PCR utilizes DNA polymerases that couple low misincorporation rates with proofreading activity to give faithful replication of the DNA target of interest.


    1. Mattila, P., et al. (1991) Nucleic Acids Research, 19, 4967–4973. PMID: 1923765
    2. Eckert, K. A., & Kunkel, T. A. (1991) Genome Research, 1, 17–24. PMID: 1842916

    VentR® is a registered trademark of New England Biolabs, Inc.
    DeepVentR™, 9°Nm™ are trademarks of New England Biolabs, Inc.