Final answer:
The spindle-assembly checkpoint, known as the M checkpoint, ensures all sister chromatids are correctly attached to spindle microtubules before cell division proceeds, safeguarding against genomic instability and ensuring accurate chromosome segregation.
Step-by-step explanation:
The spindle-assembly checkpoint, also known as the M checkpoint, is crucial for maintaining genomic stability during cell division. It occurs near the end of the metaphase stage of mitosis, where it ensures that all sister chromatids are correctly attached to the spindle microtubules before progressing to anaphase. This checkpoint involves the tension generated by the spindle fibers on the kinetochores of each chromatid pair. Once there is a firm anchoring of kinetochores to the spindle fibers arising from opposite poles, indicating proper tension levels and attachment, MPF (maturation promoting factor) initiates the activation of separase enzyme. This culminates in the separation of chromatids at their centromeres as the cell transitions to anaphase, ensuring that each daughter cell receives an accurate set of chromosomes.