The eukaryotic helicase is the Mcm2-7 heterohexamer which requires five additional accessory proteins - Cdc45 and the four subunit GINS complex – for full activity. This 11-subunit assembly is referred to as CMG (Cdc45, Mcm2-7, GINS) (Ilves et al., 2010; Moyer et al., 2006). The recent cryoEM 3D structure of S. cerevisiae CMG helicase at a DNA replication fork shows a unique DNA binding feature (Figure 1B) (Georgescu et al., 2017). Instead of encircling only ssDNA, the zinc fingers of the N-tier encircle and bind the dsDNA and the DNA unwinding point is buried inside the central channel; the unwound leading strand then proceeds through the central channel into the C-tier motor domain. The lagging strand is not visualized in the structure, indicating mobility, and is proposed to enter the initial part of the central channel defined by the N-terminal zinc fingers and then exit the surface of CMG, through a gap between two zinc fingers. The dsDNA is held at a 28° angle to the central channel, surrounded by the zinc fingers at the ‘top’ of CMG. The dsDNA appears to be tightly held because if the CMG-dsDNA contact was flexible the DNA would have been averaged out during 3D reconstruction.