The two types of proteins that control the cell cycle are internal and external regulators. Internal regulators enable the cell cycle to continue only when certain events happen, while external regulators increase or decrease the speed of the cell cycle.

Cancer is a disease that is characterized by abnormal cell growth and division. This is the disease of the cell cycle because it is caused by certain changes in a cell which prevents the cell from controlling its division.

The scientists have discovered the family of proteins which they named cyclins, that regulates the cell cycle in eukaryotic cells. These proteins bind with a certain enzyme and form a mitosis-promoting factor. The experiments showed that the cells in which the cyclins were injected during mitosis, would go through the cell cycle more quickly than the ones that were not injected with cyclins.

Cancer is a disease that is characterized by abnormal and uncontrolled cell growth and division. It is caused by certain changes in a cell which prevents the cell from controlling its division. Therefore, a drug that can modify the cell cycle of the affected cells could be very helpful in treating patients with this disease.