Introduction to the Polymerase Chain Reaction - Clinical Applications of PCR - page 1

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Introduction to the Polymerase Chain Reaction
Y. M. Dennis Lo and K. C. Allen Chan
Summary
The polymerase chain reaction (PCR) is an in vitro method for the amplification of
DNA. Since the introduction of the PCR in 1985, it has become an indispensable tech-
nique for many applications in scientific research and clinical and forensic investigations.
In this chapter, the principle and setup of PCR, as well as the methods for analyzing PCR
products, will be discussed.
Key Words: Polymerase chain reaction; PCR; principle.
1. Introduction
The polymerase chain reaction (PCR) is an in vitro method for the amplifica-
tion of DNA that was introduced in 1985 ( 1 ) . The principle of the PCR is
elegantly simple, but the resulting method is extremely powerful. The adoption
of the thermostable Taq polymerase in 1988 greatly simplified the process and
enabled the automation of PCR ( 2 ) . Since then, a large number of applications
that are based on the basic PCR theme have been developed. The versatility and
speed of PCR have revolutionized molecular diagnostics, allowing the realiza-
tion of a number of applications that were impossible in the pre-PCR era. This
chapter offers an introductory guide to the process.
2. Principle of the PCR
PCR may be regarded as a simplified version of the DNA replication process
that occurs during cell division. Basic PCR consists of three steps: thermal
denaturation of the target DNA, primer annealing of synthetic oligonucleotide
primers, and extension of the annealed primers by a DNA polymerase ( Fig. 1 ).
This three-step cycle is then repeated a number of times, each time approxi-
mately doubling the number of product molecules. The amplification factor is