What does ligase do during DNA replication?

Ligase plays a crucial role during DNA replication specifically in the process of sealing gaps between Okazaki fragments. DNA replication on the lagging strand involves the synthesis of these short segments, known as Okazaki fragments, which are created because DNA polymerase can only add nucleotides in one direction. After these fragments are synthesized, there are still gaps left between them.

Ligase is the enzyme responsible for linking these fragments together to form a continuous DNA strand. It catalyzes the formation of phosphodiester bonds between the sugar and phosphate groups of adjacent nucleotides, thereby sealing the nicks and ensuring the integrity of the DNA molecule. This step is essential for maintaining the proper structure and function of the newly synthesized DNA.

While other options in the question refer to significant processes and enzymes involved in DNA replication, they do not pertain to the specific function of ligase. For instance, the replacement of RNA primers with DNA is handled by another enzyme called DNA polymerase, while unwinding the DNA double helix is performed by helicase. Joining nucleotides to form new strands is primarily the function of DNA polymerase. Therefore, ligase’s unique role in sealing the gaps between Okazaki fragments highlights its importance in completing the