* CDK-Cyclin Complexes: CDKs are enzymes that play a crucial role in regulating the cell cycle. They are inactive on their own. To become active, they need to bind to cyclin proteins.
* Cyclin Levels: Cyclins are regulatory proteins whose levels fluctuate throughout the cell cycle. They act as "activators" for CDKs.
* Triggering Mitosis: When the concentration of specific cyclins (like cyclin B) reaches a threshold, they bind to their corresponding CDKs. This complex becomes active and initiates a cascade of events leading to the entry of the cell into mitosis.
Essentially, the CDK-cyclin complex acts as a molecular switch that signals the start of mitosis. This activation is triggered by signals outside the nucleus, like growth factors or other cues that tell the cell it's time to divide.
