DNA polymerase is a heat-stable DNA polymerase that is commonly used in the Polymerase Chain Reaction (PCR). PCR is a powerful tool for producing multiple copies of a specific DNA fragment in a short amount of time. It involves a series of temperature cycles that separate the DNA strands, anneal primers to the target sequence, and extend the primers. The assembly of the new strands is carried out by the enzyme DNA polymerase. DNA polymerase is a technique used to make many copies of a selected DNA sequence.

The DNA is loaded into a PCR machine in which a cycle of steps repeatedly doubles the quantity of the selected DNA. This involves double-stranded DNA being separated into two single strands at one stage of the cycle and single strands combining to form double-stranded DNA at another stage. If DNA is heated to a high temperature, the hydrogen bonds eventually break and the two strands separate. This is called re-annealing. The two strands in DNA are held together by hydrogen bonds.

The enzyme Taq DNA polymerase is used to break DNA strands into single-stranded DNA. It was obtained from a bacterium, Thermus aquaticus, found in hot springs, including those of Yellowstone National Park. At 95 °C it adds about 1,000 nucleotides per minute, a very rapid rate of DNA replication. A cycle of PCR can be completed in less than two minutes.