sentences:  Once the Mcm proteins have been loaded onto the chromatin, ORC and Cdc6 can be removed from the chromatin without preventing subsequent DNA replication.This observation suggests that the primary role of the pre-replication complex is to correctly load the Mcm proteins.The Mcm proteins on chromatin form a head-to-head double hexamer with the two rings slightly tilted, twisted and off-centred to create a kink in the central channel where the bound DNA is captured at the interface of the two rings.