Methods (molecular, IHC, frozen)
PCR reaction stages

Topic Completed: 1 July 2010

Minor changes: 15 February 2019

Copyright: 2008-2018,, Inc.

PubMed Search: PCR reaction[TIAB] stages

Rodney E. Shackelford, D.O., Ph.D.
Page views in 2020: 85
Table of Contents
Definition / general
Cite this page: Shackelford R. PCR reaction stages. website. Accessed January 18th, 2021.
Definition / general
  • Thermocycles in PCR can be divided into three stages
  • Understanding where each of these stages occurs in each PCR reaction is important, especially for the analysis of end point PCR reactions

Exponential amplification:
  • Initially, all the reagents employed (primers and nucleoside triphophates) in PCR are abundant and the Taq polymerase is fully functional
  • Therefore the initial phases of PCR are characterized by near 100% efficient DNA amplification, with the amount of replicated DNA doubled per thermocycle

Leveling off stage:
  • In later thermocycles the Taq polymerase begins to lose its activity and the concentration of primers and nucleoside triphophates become rate limiting, hence the reaction rat significantly slows

  • Eventually no new DNA amplification occurs due to exhaustion of the reagents and loss of enzyme activity
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