The spindle assembly checkpoint (SAC) is a crucial mechanism in cell division that ensures chromosomes are properly aligned and attached to the spindle apparatus before proceeding with mitosis. This checkpoint prevents errors during cell division, which can lead to aneuploidy, a condition where cells have an abnormal number of chromosomes. During the SAC, proteins detect whether all chromosomes are correctly attached to the spindle microtubules. If any chromosomes are not properly aligned, the checkpoint halts the cell cycle, allowing time for corrections. This process is vital for maintaining genetic stability in daughter cells, ultimately contributing to the overall health of an organism.