Molecular - PCR - Taq polymerase

Home Chapter Home Jobs Conferences Fellowships Books

Molecular Pathology

Polymerase Chain Reaction

Taq Polymerase

Author: Rodney E. Shackelford, D.O., Ph.D. (see Reviewers page)

Revised: 8 July 2010, last major update July 2010

General

=========================================================================

● Initially the Klenow fragment from the E. coli DNA polymerase I was used in PCR reactions

● While the Klenow fragment worked in PCR, it rapidly denatured at the 90°C or higher temperatures required for denaturation, requiring the addition of new Klenow polymerase after every denaturation step

● The need to open the reaction chamber with every PCR thermocycle made PCR cumbersome and greatly increased the chances for contamination with unwanted DNA

● The solution to this problem came from the discovery and cloning of a thermostable DNA polymerase from the thermophilic bacterium Thermus aquaticus

● The polymerase, known as the Taq polymerase, has many attributes that are well suited for PCR:

● (a) the enzyme works best at 75-80°C, allowing the elongation step to occur at temperatures which make non-Watson-Crick base paring a rare event

● (b) its half-life at 95°C is over 40 minutes

● (c) at 72°C it can add 1,000 nucleoside triphosphates to a growing DNA strand

● Most PCR reactions done with Taq can be completely closed through all the thermocycles

● Taq lacks 3' to 5' exonuclease proofreading activity, allowing a roughly 1 per 9,000 error rate in nucleoside triphosphate incorporation

● Additionally, Taq often adds an adenine to the end of its polymerase reaction (sometimes used to facilitate TA cloning)

● Taq was named “The Molecule of the Year” by Science in 1989

End of Molecular Pathology > Polymerase Chain Reaction > Taq polymerase

This information is intended for physicians and related personnel, who understand that medical information is often imperfect, and must also be interpreted in the context of a patient's clinical data using reasonable medical judgment. This website should not be used as a substitute for the advice of a licensed physician.

All information on this website is protected by copyright of PathologyOutlines.com, Inc. Information from third parties may also be protected by copyright. Please contact us at copyrightPathOut@gmail.com with any questions (click here for other contact information).