Final answer:
Taq DNA polymerase is used in PCR because it is thermostable, meaning it can withstand the high temperatures required during the cycles of DNA amplification without denaturing, making it more efficient than other enzymes that would require replenishment after each cycle.
Step-by-step explanation:
DNA polymerase from Thermus aquaticus (Taq) is used in polymerase chain reaction (PCR) instead of DNA polymerase from a human or other bacteria due to its remarkable ability to withstand high temperatures. The enzyme, Taq polymerase, is crucial because PCR involves repeated cycles of heating and cooling, which typically denature enzymes. Taq polymerase, with an optimal temperature of 72°C and active in ranges from 22°C to 89°C, remains stable through PCR's demanding thermal cycles. This means that instead of adding a new enzyme after each cycle, as would be necessary with less thermostable enzymes, a single addition of Taq polymerase at the beginning can suffice for the entire process.
The discovery of Taq polymerase, a thermostable enzyme, has greatly streamlined DNA sequencing and amplification, making PCR automation possible with the use of programmable thermocyclers. This advancement came from thermophiles like T. aquaticus, which can thrive in extreme heat, such as the hot springs of Yellowstone National Park, where temperatures exceed the typical survivable range for most life forms. The durability of Taq polymerase thus aligns perfectly with the conditions required for PCR, making it an invaluable tool for generating millions of copies of a specific DNA segment.