Polymerase
Chain Reaction
(PCR)
PCR
involves a series of thermal cycles, each resulting in denaturation
of a double-stranded DNA target. Denaturation reduces the DNA to two
single strands, (usually at around 94 degrees C). The temperature
is then lowered and oligonucleotide primers are introduced to the
solution. The process of annealing then follows, where the primers
bind to the appropriate sites on the single stranded DNA. Specific
enzymes (thermostable DNA polymerises) then synthesize the complimentary
DNA strand along the single strand target segment. This process of
extension is complete when the enzymes have synthesized the entire
DNA strand, and the resulting solution now contains two daughter double-stranded
DNA segments for every original segment.
Many
repetitions of the process soon amplify enough DNA with which to sequence.
Successful amplification is dependant on the efficient interaction of
many components, most of which can be optimised for a given target DNA
(Palumbi 1996).