What enzyme seals gaps between Okazaki fragments during DNA replication?

During DNA replication, the process involves the synthesis of new DNA strands by enzymes, with lagging strands created in segments known as Okazaki fragments. These fragments are produced because DNA polymerase can only add nucleotides in a 5’ to 3’ direction. As a result, after the synthesis of these fragments, there are gaps between them that need to be sealed to create a continuous DNA strand.

The enzyme responsible for sealing these gaps is ligase. DNA ligase catalyzes the formation of phosphodiester bonds between the adjacent nucleotides of the Okazaki fragments, effectively linking them together. This action is crucial for maintaining the integrity of the newly synthesized DNA and ensuring its proper functionality.

While helicase unwinds the DNA double helix, single-strand binding proteins stabilize the unwound DNA strands during replication, and topoisomerase alleviates the supercoiling ahead of the replication fork, none of these enzymes are involved in the direct sealing of Okazaki fragments. Thus, ligase is specifically identified as the enzyme that completes the DNA replication process on the lagging strand by linking the fragments, making it the correct response.