Figure 1
From: A Dynamical Model for Activating and Silencing the Mitotic Checkpoint

Schematic illustration of SAC activity. Unattached kinetochores (red in the middle of the chromosomes) catalyze the formation of MCC which inhibits the Cdc20-activated APC/C. Once all kinetochores are attached (green) the APC/C ubiquitinates Securin and CyclinB, resulting in the destruction of Cohesin by Separase. Unblocked Cdk1 initiates metaphase and progress in the cell cycle.