A DNA helicase, powered by ATP hydrolysis, propels itself rapidly along one of the template DNA strands (here the lagging strand), forcing open the DNA helix ahead of the replication fork.

Mechanism of PCNA loading by Ctf18-RFC for leading-strand DNA synthesis. Science, 2024; 385 (6708) DOI: 10.1126/science.adk5901 Qing He, Feng Wang, Michael E. O’Donnell, Huilin Li.

The polymerase on the “leading strand” can easily work at a continuous pace, but the polymerase on the “lagging strand” cannot. Until now, scientists believed that the polymerases on the ...