Which checkpoint allows progression to the M phase if DNA replication is undamaged?

The G2 checkpoint is a critical control point in the cell cycle that specifically assesses whether DNA replication has been completed accurately and without damage before the cell proceeds to enter the M phase (mitosis). If the DNA is intact and properly duplicated, cell cycle regulatory mechanisms allow progression into mitosis. This checkpoint functions to prevent the division of cells that have damaged or incompletely replicated DNA, thereby maintaining genomic stability.

In contrast, the other checkpoints serve different purposes. The G1 checkpoint assesses cell size, nutrient availability, and overall cellular health before allowing progression into the S phase, where DNA replication occurs. The S checkpoint monitors the integrity of DNA during replication itself. The M checkpoint, on the other hand, ensures that all chromosomes are properly attached to the mitotic spindle before the cell divides, rather than checking the status of DNA replication.

Thus, the G2 checkpoint plays a pivotal role in ensuring that only cells with undamaged and fully replicated DNA move into the M phase, supporting the proper progression of the cell cycle.