What role does gyrase play during DNA replication?

The correct answer highlights the essential function of gyrase in the context of DNA replication. Gyrase is a type II topoisomerase that plays a critical role in managing the torsional strain that occurs ahead of the replication fork due to the unwinding of DNA. As DNA helicase unwinds the double helix to allow replication, it creates positive supercoiling ahead of the fork. Gyrase alleviates this strain by introducing negative supercoils into the DNA, effectively relaxing the positive supercoils. This process is vital for the continuation of replication as it prevents the DNA from becoming overly twisted and potentially breaking.

The other options do not align with the function of gyrase. RNA primase is responsible for synthesizing RNA primers for DNA replication but is not related to the action of gyrase. Degradation of RNA strands typically pertains to RNAse activity, which does not involve gyrase's role in DNA topological changes. Lastly, the ligation of DNA fragments is facilitated by DNA ligase, not gyrase, which is focused on managing supercoiling rather than connecting DNA fragments.