Explain the role of ligase in DNA replication.

Ligase plays a crucial role in DNA replication, particularly in the process of joining separate segments of DNA that are synthesized discontinuously on the lagging strand. During replication, the lagging strand is synthesized in short fragments called Okazaki fragments. These fragments are produced as the DNA polymerase works away from the replication fork, adding nucleotides until it reaches the preceding fragment.

Once these Okazaki fragments are synthesized, they need to be connected to form a continuous DNA strand. This is where ligase comes in. Ligase catalyzes the formation of phosphodiester bonds between the 3' end of one Okazaki fragment and the 5' end of the adjacent fragment, thereby sealing the gaps and completing the DNA strand.

This connection is vital for maintaining the integrity of the newly synthesized DNA, ensuring that it is a seamless double helix. Without the action of ligase, the lagging strand would remain fragmented, leading to incomplete and dysfunctional DNA molecules.