Question

One explanation for why DNA polymerase can only synthesize in one direction is the effect in would have on proofreading . What would happen if an incorrect nucleotide synthesized at the 5' end by a hypothetical polymerase were removed?

(A) The polymerase would not be able to add another nucleotide to the 5' end because there would be no template
(B) The polymerase would not be able to add another nucleotide to the 5' end because there would not be a phosphoanhydride bond to cleave for the coupled reaction
(C) The polymerase would not be able to add another nucleotide to the 5' end because there is no phosphate
(D) All of the above

Answer 1

If an incorrect nucleotide were synthesized at the 5' end by a hypothetical polymerase, the polymerase would not be able to add another nucleotide to the 5' end because there would not be a phosphoanhydride bond to cleave for the coupled reaction.

Step-by-step explanation:

DNA polymerase can only synthesize in the 5' to 3' direction because it requires a free 3'-OH group to which it can add nucleotides. If an incorrect nucleotide were to be synthesized at the 5' end by a hypothetical polymerase, there would not be a phosphoanhydride bond to cleave for the coupled reaction, so the polymerase would not be able to add another nucleotide to the 5' end. Therefore, the correct answer is (B) The polymerase would not be able to add another nucleotide to the 5' end because there would not be a phosphoanhydride bond to cleave for the coupled reaction.