Which enzyme is crucial for sealing the repaired gaps during the DNA repair process?

DNA ligase is fundamental in sealing the repaired gaps during the DNA repair process. Its primary function is to join together the 3' hydroxyl end of one DNA strand with the 5' phosphate end of another, facilitating the formation of a phosphodiester bond. This process is especially critical during DNA replication and repair when there are nicks or breaks in the DNA backbone.

In the context of DNA repair, after other enzymes, such as DNA polymerases, have filled in the missing sections of DNA, DNA ligase ensures that the newly synthesized segments are ligated to the existing strand, completing the repair and restoring the DNA to its intact state. Without the action of DNA ligase, the repaired DNA would be left with discontinuities, leading to potential genomic instability.

Other enzymes mentioned—such as helicase, polymerase, and topoisomerase—perform various roles in DNA metabolism, but they do not participate directly in the sealing of nicks in the DNA. Helicase unwinds the DNA double helix, polymerase synthesizes new DNA strands by adding nucleotides, and topoisomerase alleviates torsional strain during DNA unwinding. However, it is ligase that specifically performs the essential function of