What is the function of topoisomerase during DNA replication?

Topoisomerase plays a critical role during DNA replication by alleviating the tension that builds up in the DNA helix as it unwinds. As helicase unwinds the double-stranded DNA, it creates torsional strain ahead of the replication fork. Topoisomerases work to manage this strain by introducing temporary breaks in the DNA strands, allowing them to unwind and rotate freely, thus preventing excessive supercoiling. This relaxation of the twisting of the DNA helix is essential for the smooth progression of replication, ensuring that the DNA strands can separate adequately for the replication machinery to function effectively.

In contrast, other functions like joining Okazaki fragments are specific to DNA ligase, unwinding the DNA strands is primarily the role of helicase, and proofreading DNA sequences is the responsibility of DNA polymerases during replication.