Final answer:
Topoisomerase is the enzyme responsible for relieving the pressure from supercoiling in DNA during replication by breaking and rejoining the phosphate backbone of the DNA ahead of the replication fork. This process helps to prevent damage to the DNA and ensures smooth replication process.
Step-by-step explanation:
The enzyme responsible for relieving the pressure that results from supercoiling during DNA replication is called topoisomerase. This enzyme functions by creating transient breaks within the phosphate backbone of the DNA molecule, ahead of the replication fork. By doing so, it effectively relaxes the tension generated by the unwinding process. Topoisomerases carry out their function by catalyzing the cleavage and re-ligation of these breaks, allowing the DNA to relieve torsional strain and preventing damage such as breakage or unwanted supercoiling.
During replication, unwinding DNA creates positive supercoiling ahead of the replication fork, which, if not relieved, would result in increasing tension within the DNA molecule. Topoisomerase, sometimes referred to as DNA gyrase in bacteria, can introduce a temporary cut in the DNA strands, permitting the helix to spin and unwind, thus reducing the supercoiling. This ensures the continuity and fidelity of the replication process by allowing the DNA helicase and other replication machinery to advance without being hindered by supercoiled DNA.
The action of topoisomerase is critical because increased DNA unwinding could otherwise cause the phosphodiester bonds in the DNA to rupture, leading to DNA fragmentation. Therefore, topoisomerases such as DNA gyrase provide a necessary function in DNA replication and cell division.