Taq is an enzyme that has impacted molecular biology. This enzyme is central to a laboratory technique for making many copies of specific DNA segments. Its unique properties have made it an indispensable tool for scientific and medical applications.
What Taq Stands For
“Taq” is an abbreviation for Thermus aquaticus, a bacterium discovered in hot springs. Scientists isolated Thermus aquaticus from a hot spring in Yellowstone National Park in the late 1960s. This bacterium thrives in environments with temperatures around 70°C (158°F), much hotter than most other known organisms.
Taq polymerase is the enzyme derived from this heat-loving bacterium. A polymerase is an enzyme that synthesizes long chains of molecules, particularly DNA. DNA polymerases build new DNA strands by adding individual building blocks, called nucleotides, using an existing DNA strand as a template.
The Unique Nature of Taq Polymerase
Taq polymerase possesses a unique characteristic known as thermophilicity, or heat stability. Most enzymes lose their structure and function, a process called denaturation, at temperatures above 60-70°C (140-158°F). In contrast, Taq polymerase remains active and stable even at temperatures near boiling, such as 94-98°C (201-208°F).
This remarkable heat resistance is directly linked to its origin in hot springs. The enzyme’s ability to withstand repeated heating and cooling cycles without denaturing is an advantage. This property allows it to function effectively in processes that involve significant temperature fluctuations.
Taq’s Indispensable Role in Biotechnology
Taq polymerase is essential for the Polymerase Chain Reaction (PCR), a fundamental technique in molecular biology. PCR enables scientists to rapidly create millions of copies of a specific DNA segment from a very small initial amount. The process involves repeated cycles of temperature changes in a thermal cycler.
A typical PCR cycle includes three main steps: denaturation, annealing, and extension. During denaturation, the DNA sample is heated to 94-98°C (201-208°F) to separate the double-stranded DNA into two single strands. Taq’s heat stability prevents the enzyme from being destroyed by these high temperatures.
Next, the temperature is lowered to allow short DNA primers to attach to specific regions on the single DNA strands, a step called annealing. Finally, during the extension phase, the temperature is raised to approximately 72°C (162°F), and Taq polymerase synthesizes new DNA strands by adding nucleotides to the primers. This cycle is repeated 20-40 times, exponentially amplifying the DNA.
The widespread use of PCR, made possible by Taq polymerase, has had a broad impact across many scientific disciplines. In forensics, PCR is used for DNA fingerprinting to identify individuals from trace amounts of DNA evidence. In medicine, it aids in diagnosing infectious diseases by detecting viral or bacterial DNA, and helps identify genetic disorders and certain cancers. PCR is also fundamental in genetic research for studying gene expression, identifying genetic mutations, and in DNA sequencing.