ABSTRACT
The polymerase chain reaction (PCR) is an in vitro method for amplification of DNA sequences. PCR can be applied to DNA recovered from environmental samples. Because of the amplification power of PCR, it is critical to avoid even a trace of contamination with DNA containing the target sequence. The product of each PCR cycle is complementary to and capable of binding primers, so that the amount of DNA synthesized is doubled in each successive cycle. The essential reagents for PCR are a thermostable DNA polymerase, oligonucleotide primers, deoxynucleotides (dNTPs), template (target) DNA, and magnesium ions. The heat-stable DNA polymerase retains activity through sufficient PCR cycles to achieve better than 1 million-fold amplification of the target DNA sequence. PCR-amplified DNA can be analyzed by various methods including gel electrophoresis and hybridization techniques. The method of detection selected depends upon the sensitivity required and whether additional information such as size of the amplified DNA is also to be determined in the analysis.
