This image provided by David Barford for day 317 of #LMB365 shows the cryo-EM structure of the anaphase-promoting complex (APC/C) (surface representation) bound to its inhibitor, the mitotic checkpoint complex (MCC) (ribbons representation). The MCC exerts the spindle assembly checkpoint during mitosis to coordinate APC/C activity with the correct attachment of all chromosomes to the mitotic spindle. This ensures faithful chromosome segregation and prevents aneuploidy, a causative factor in cancer and congenital defects.