Which enzyme unwinds DNA during replication?

Helicases are a class of enzymes that are vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic double helix, separating the two hybridized nucleic acid strands, via the energy gained from ATP hydrolysis. There are many helicases, representing the great variety of processes in which strand separation must be catalyzed. Approximately 1% of eukaryotic genes code for helicases.