Question

Enzyme 'Tag polymerase' used in $PCR$, has been isolated from bacterium

• A. Agrobacterium tumefaciens
• B. Thermus aquaticus
• C. Streptomyces albus
• D. Escherichia coli

Answer 1

Answer: (B)

The final step of $PCR$ is extension, wherein Taq $DNA$ polymerase (isolated from a thermophilic bacterium Thermus aquaticus) synthesises the $DNA$ region between the primers, using $DNTPs$ (deoxynudeoside triphosphates) and $M{g}^{2+}$. The primers are extended towards each other so that the $DNA$ segment lying between the two primers is copied. The optimum temperature for this polymerisation step is $72^{°}C$. Taq polymerase remains active during high temperature induced denaturation of double stranded $DNA$.