sentences:  The importance of this direct link between the helicase and the leading-strand polymerase is underscored by results in cultured human cells, where Mrc1/Claspin is required for efficient replication fork progression.These results suggest that efficient DNA replication also requires the coupling of helicases and leading-strand synthesis...
  
  DNA polymerases require additional factors to support DNA replication.DNA polymerases have a semiclosed 'hand' structure, which allows the polymerase to load onto the DNA and begin translocating.