Which checkpoint in the cell cycle is responsible for checking chromosome attachment to the spindle?

The M checkpoint, also known as the spindle assembly checkpoint, plays a critical role in ensuring that all chromosomes are properly attached to the spindle apparatus before the cell proceeds with division. This checkpoint occurs during the metaphase stage of mitosis, where the cell checks for the correct alignment and attachment of chromosomes to the spindle fibers, which is essential for accurate segregation of the genetic material into the daughter cells.

If the chromosomes are not attached correctly, the M checkpoint will halt the cell cycle, preventing progression to anaphase. This mechanism is vital for maintaining genomic stability and preventing errors in cell division that could lead to aneuploidy, where daughter cells have an abnormal number of chromosomes, increasing the risk of tumorigenesis.

The importance of the M checkpoint is underscored by the fact that once the cell has passed this point, it commits to completing mitosis. This ensures that any potential errors in chromosome attachment are corrected before the cell divides, maintaining the integrity of the organism's genome.