If a researcher used Escherichia coli DNA polymerase instead of Thermus aquaticus DNA polymerase in the PCR procedure, what would be the result? A. PCR would occur twice as fast as normal B. PCR would stop after one cycle C. Many mistakes would occur D. PCR would not occur at all E. PCR would occur more slowly than normal

If a researcher used Escherichia coli DNA polymerase instead of Thermus aquaticus DNA polymerase in the PCR procedure, what would be the result?
A. PCR would occur twice as fast as normal
B. PCR would stop after one cycle
C. Many mistakes would occur
D. PCR would not occur at all
E. PCR would occur more slowly than normal

Answer

• B. PCR would stop after one cycle
  Explanation:
  PCR involves three main steps, which are denaturation, annealing, and elongation. PCR begins with an initial step of breaking the double-stranded DNA using a temperature of 94 degrees Celsius. The next step is allowing the annealing of the DNA polymerase on primers. For a normal enzyme, it is during this stage that duplication of the DNA occurs for the first round. However, for taq polymerase, the temperature has to be raised to between 70 and 74 degrees Celsius for duplication to occur. By this temperature, E.Coli DNA polymerase will have been deactivated and hence cannot duplicate DNA any further. Thus, using E.Coli DNA in PCR would only duplicate DNA one cycle and stop after deactivation.