Final answer:
DNA gyrase or topoisomerase II cuts and reseals the DNA phosphate backbone to relieve the positive supercoiling that occurs as a result of DNA unwinding during replication. Without topoisomerase activity, increased torsional strain could impair replication and damage DNA.
Step-by-step explanation:
DNA gyrase, also known as topoisomerase II, plays a critical role in DNA replication by reducing the positive supercoiling or torsional strain that occurs ahead of the replication fork. This enzyme works by cutting the DNA's phosphate backbone, allowing the DNA strands to unwind and relieve the supercoiling tension. Then, DNA gyrase reseals the backbone, maintaining the integrity of the DNA molecule.
Without the action of topoisomerase II, the accumulation of positive supercoiling would increase the torsional strain and eventually hinder the movement of the replication fork. This could lead to errors in DNA replication or even halt the process altogether, potentially causing DNA damage or cell death as a result of improper DNA replication. The enzyme's activity is vital for allowing DNA replication to proceed smoothly by managing the structural stress on the DNA.
DNA changes shape, during replication and enzymes such as helicase and topoisomerase are necessary to facilitate this process. Helicase unwinds the DNA at the origin of replication, generating tension that is relieved by topoisomerase II, which relaxes the supercoiled chromosome and manages the supercoiling during replication.