Polymerase Chain Reaction PCR reaction stages Author: Rodney E.
Shackelford, D.O., Ph.D. (see Reviewers page) Revised: 22
September 2012, last major update July 2010 Copyright: (c)
2008-2010, PathologyOutlines.com, Inc. ● The 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 ●
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 e