What could happen if cell cycle checkpoints are not functioning properly?

When cell cycle checkpoints are not functioning properly, the regulation of the cell cycle is compromised. Checkpoints are critical control mechanisms that monitor and regulate the progression of a cell through the various phases of the cell cycle, ensuring that any potential errors in DNA replication or damage are addressed before the cell divides. If these checkpoints fail, cells can continue to divide unchecked, which can lead to uncontrolled cell division. This uncontrolled growth is a hallmark of cancer, as it allows for the accumulation of mutations and abnormalities that can further drive cancerous transformations.

In contrast, scenarios such as normal cell growth, controlled cell division, or increased cell apoptosis are less likely to occur when cell cycle checkpoints are impaired. Normal cell growth and controlled division are dependent on the proper functioning of these checkpoints to prevent errors during division. Increased apoptosis may occur in some cases where cells are damaged, but when checkpoints malfunction, it is instead the lack of apoptotic signals that contributes to the survival and proliferation of cells that should not be dividing. Hence, the primary concern with dysfunctional checkpoints is the potential onset of cancerous growth due to unchecked cell division.