The DNA Polymerase Used in PCR Comes from the Bacterium

Multiple Choice

The DNA polymerase used in PCR comes from the bacterium thermophile Thermus aquaticus, and is called Taq polymerase. Why is this enzyme used, and not a DNA polymerase from an organism such as E. coli?

A) The DNA synthesis step of the PCR cycle occurs at 95ᵒC; Taq polymerase is from a bacterium that grows in high temperatures and can function at this temperature, while DNA polymerase from a mesophile such as E. coli would be denatured at this temperature.
B) The DNA synthesis step of the PCR cycle occurs at 72ᵒC; Taq polymerase can function at this temperature, while DNA polymerase from a mesophile such as E. coli requires significantly higher temperatures in order to function correctly.
C) E. coli is an RNA organism and therefore depends on RNA polymerase for its replication cycle; it is not possible to obtain DNA polymerase from this bacterium.
D) The DNA synthesis step of the PCR cycle occurs at 72ᵒC; Taq polymerase is from a bacterium that grows in high temperatures and can function at this temperature, while DNA polymerase from a mesophile such as E. coli would be denatured at this temperature.
E) DNA polymerase from Thermus aquaticus is a very active enzyme. It is able to synthesize DNA at a faster rate than any other known DNA polymerase which is important because the key to successful PCR is a speedy reaction.