Taq Polymerase - Taq Polymerase in PCR

Taq Polymerase in PCR

In the early 1980s, Kary Mullis was working at Cetus Corporation on the application of synthetic DNAs to biotechnology. He was familiar with the use of DNA oligonucleotides as probes for binding to target DNA strands, as well as their use as primers for DNA sequencing and cDNA synthesis. In 1983, he began using two primers, one to hybridize to each strand of a target DNA, and adding DNA polymerase to the reaction. This led to exponential DNA replication, greatly amplifying the amounts of DNA between the primers.

However, after each round of replication the mixture needs to be heated above 90°C to denature the newly formed DNA, allowing the strands to separate and act as templates in the next round of amplification. This heating step also inactivates the DNA polymerase that was in use before the discovery of Taq polymerase, the Klenow fragment of the DNA Polymerase I from E. coli.

Use of the thermostable Taq polymerase eliminates the need for having to add new enzyme to the PCR reaction during the thermocycling process. A single closed tube in a relatively simple machine can be used to carry out the entire process. Thus, the use of Taq polymerase was the key idea that made PCR applicable to a large variety of molecular biology problems concerning DNA analysis.