Used to amplify dna fragments without bacterial cells. Adapted to rna templates by converting them to complementary dnas using reverse transcriptase. Technique uses a heat-stable dna polymerase, called taq polymerase, isolated from a bacterium living in hot springs above 90 degrees celsius. The oligonucleotides are primers were nucleotides are added during replication steps. The mixture is heated to about 95 degrees celsius which is enough heat to separate the dna molecules into their two component strands. The mixture is cooled to about 60 degrees celsius so primers hybridize to the strands of the target. The temperature is raised to about 72 degrees celsius to allow thermophilic polymerase to add nucleotides to the 3" end of the primers. As the polymerase extends the primer, it copies the target dna, forming new complementary. The temperature is raised again so the newly formed and original dna strands separate from another.
