B IO C H E M IS T R Y PE A R L S
Polymerase chain reaction (PCR) is an in vitro method for the expo-
nential amplification of a specific DNA region.
PCR involves (1) denaturation, which separates the two DNA chains
by heating the reaction mixture to 90°C to 95°C (194°F to 203°F);
(2) annealing or cooling to 45°C to 60°C (113°F to 140°F) so that
the oligonucleotide primers can bind or anneal to the separated
strands of the target DNA; and (3) elongation with DNA poly-
merase (at 72°C [162°F] when
DNA polymerase used)
adding nucleotides to the 3' ends of the primers to a complete
copy of the target DNA template.
GC pairs have three hydrogen bonds, whereas AT pairs have only
two hydrogen bonds and are therefore weaker.
A heat-stable DNA polymerase obtained from the thermophilic bac-
is used to synthesize the new strands in most
Endonucleases usually act at sites of palindromes.
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Biochemistry, 26th ed. New York: Lange Medical Books/McGraw-Hill, 2003.
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tion and species identification of human herpesviruses. J Clin Microbiol 2000;