Question

Which of the following is/are required for the polymerization reaction catalyzed by DNA polymerase III?

Answer 1

Answer:

D. I, IV, VI, and VII

Explanation:

DNA polymerase III has both 5' to 3' polymerization activity and 3' to 5' exonuclease activity (the proofreading). DNA pol III requires divalent magnesium ions for its polymerization and proofreading activities. Here, the magnesium ions serve as cofactor.

DNA polymerase III cannot start the process of synthesis of new DNA strand de novo and uses an RNA primer synthesized by primase enzyme. The polymerization activity of DNA polymerase III elongates the RNA primer in 5' to 3' direction. The primers are removed by 5' to 3' exonuclease activity of DNA polymerase I.

During polymerization, the DNA polymerase III uses existing DNA strand as a template. The four dNTPs namely deoxyadenosine triphosphate (dATP), deoxycytidine triphosphate (dCTP), deoxyguanosine triphosphate (dGTP) and deoxythymidine triphosphate (dTTP) are added to the RNA primer according to the sequence of DNA template.