3) Their work suggests an MCM10-dependent switching of the CMG between a double-stranded to single-stranded mechanism upon encountering a roadblock. But given the performance advantage of MCM10 on the CMG and, as the authors state, the persistence of MCM10 at forks, why should the CMG not always occupy this functional state, i.e. steric exclusion without ever occupying the (intermediate?) state they observe by EM. This should be discussed as a speculation. On the other hand direct biophysical or structural data provided.