Question

In addition to the Taq polymerase enzyme, which other thermostable DNA polymerases have been isolated to be used in a polymerase chain reaction (PCR) ?
(a) Pfu polymerase isolated from Pyrococcus furiosus
(b) Tli polymerase (vent polymerase) isolated from Thermococcus litoralis
(c) Both (a) and (b)
(d) None of these

Answer 1

In addition to the Taq polymerase enzyme, the PCR reaction usually uses two other enzymes as a thermostable DNA polymerase. The B DNA polymerase family belongs to one of them. These enzymes have an activity for proof-reading.

Complete answer:
Pfu polymerase and Tli polymerase, which are both thermostable, have been isolated, in addition to Tag DNA polymerase. Isolated from Pyrococcus furiosus is Pfu polymerase. Isolated from Thermococcus litoralis is Tli (vent) polymerase.
The use of the thermostable Taq allows the PCR to be worked at high temperatures, thereby promoting the high specificity of the primers and reducing the output of non-specific products, such as primer dimers. The use of a thermostable polymerase also removes the need for each round of thermocycling to incorporate a new enzyme. To carry out the whole operation, a single closed tube in a relatively simple machine can be used. The use of Taq polymerase was therefore the main concept that made PCR relevant to a wide range of DNA research issues in molecular biology.
Pfu DNA polymerase is an enzyme found in the Pyrococcus furiosus hyperthermophilic archaeon, where it acts during cell division to copy the DNA of the organism. In the laboratory setting, Pfu is used in the polymerase chain reaction (PCR) to amplify DNA, where the enzyme serves the central purpose of copying a new DNA strand during each stage of extension.
A high-fidelity thermophilic DNA polymerase is Tli DNA Polymerase (also referred to as Vent DNA Polymerase). Tli DNA Polymerase fidelity is 5-15-fold greater than that observed for Taq DNA Polymerase. After a 1-hour incubation at 95 degrees Celsius, greater than 90 percent of the polymerase activity remains. Vent polymerase is a DNA polymerase that is thermostable and used for the polymerase chain reaction. The thermophilic Thermococcus litoralis was used for its isolation.

Additional information: Taq polymerase, named after the thermophilic eubacterial microorganism Thermus aquaticus , is a thermostable DNA polymerase. Originally, Chien et al isolated it in 1976. Often, its name is abbreviated to Taq or Taq pol. It is also used in the reaction of the polymerase chain (PCR), a mechanism for greatly amplifying the number of short DNA segments.
So the correct answer is, ‘both a and b’.

Note: Polymerase chain reaction (PCR) is a process commonly used to produce millions to billions of copies of a particular DNA sample quickly, enabling scientists to take a very small DNA sample and amplify it to a sufficient amount to be examined in depth. A DNA polymerase is an important component of PCR; an enzyme that polymerizes new DNA strands; particularly common is the heat-resistant Taq polymerase, as it is more likely to remain intact throughout the denaturation phase of high-temperature DNA.