Checkpoints are the processes that regulate cell growth and division in the cell cycle, and their malfunction can lead to uncontrolled growth and cancer.
The processes during the cell cycle that ensure appropriate cell growth and rates of division are the internal controls known as checkpoints. There are three main checkpoints: one at the end of the G1 phase, a second at the G2/M transition, and the third during metaphase. These checkpoints use signaling proteins such as cyclins and cyclin-dependent kinases (Cdks), as well as tumor suppressor proteins, to regulate the cell cycle. A malfunction at these checkpoints can lead to uncontrolled growth and cancer due to errors in the cell cycle regulation.