Question

Repair of an apurinic or apyrimidinic site in DNA by AP endonuclease must be completed by the action of _________.

1) UvrABC endonuclease
2) RecA protein
3) DNA polymerase I
4) None of the choices are correct

Answer 1

To repair an apurinic or apyrimidinic site in DNA after AP endonuclease action, DNA polymerase I adds the correct nucleotide and DNA ligase seals the site by creating a phosphodiester bond.

Step-by-step explanation:

The repair of an apurinic or apyrimidinic site (AP site) in DNA requires a series of steps and multiple enzymes. After an AP endonuclease creates a nick at the AP site, the completion of the repair process involves the collaborative action of additional enzymes. DNA polymerase I is responsible for adding the correct nucleotide to the 3' end of the nick created by the AP endonuclease.

Once the correct nucleotide is added, DNA ligase is required to seal the repair by creating a phosphodiester bond, completing the backbone of the DNA. The response to the student's question is then: Repair of an apurinic or apyrimidinic site in DNA by AP endonuclease must be completed by the action of 3) DNA polymerase I.