Question

The thermostable enzymes, 'Taq' and 'Pfu', isolated from thermophilic bacteria are.
A. RNA polymerase
B. DNA polymerase
C. Restriction endonuclease
D. DNA ligases

Answer 1

Hint: Taq is an enzyme isolated from Thermus aquaticus and Pfu is found in Pyrococcus furiosus. Both are referred to as DNA synthesizing enzymes.

Complete Answer:
- DNA polymerase is the enzyme that synthesizes a new strand of DNA that is complementary to the parent strand. This polymerase is responsible for DNA replication in the living cell.
- Polymerase chain reaction (PCR) is an artificial means of producing millions to billions of copies of DNA and it requires high temperature.
- But a cell's DNA polymerase cannot withstand high temperatures up to 72°C. Taq DNA polymerase and Pfu DNA polymerase are thermostable up to °C.
- Therefore Taq and Pfu are used in the PCR.

Hence, the correct answer is option B. DNA polymerase.

Additional information: Taq has polymerase activity in 5'-3' direction, but unlike cell's DNA polymerase Taq does not have exonuclease proofreading activity of 3' to 5', this lowers the replication fidelity by a big margin.
- DNA polymerase can identify mistakes in one in every billion base pairs that are copied, this proofreading activity of DNA polymerase makes it unique than other identified DNA polymerases.
- It preserves the integrity of the original DNA strand that is passed onto the daughter cells and also lowers the mutation rate.

Note: Taq and Pfu are also known as Taq polymerase and Pfu. Taq polymerase can replicate a 1000 base pair strand of DNA in less than 10 seconds at 72 °C.