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Sculptures by Phyllis Bone

Polymerase Chain Reaction

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).