What role do cyclins play in the cell cycle?

Cyclins play a crucial role in regulating the progression of the cell cycle by activating cyclin-dependent kinases (CDKs). These proteins are essential for the proper timing of the cell cycle events, including DNA replication and cell division. When cyclins bind to CDKs, they trigger a series of phosphorylation events that drive the cell through various phases of the cell cycle. Each phase has specific cyclins that bind to their corresponding CDKs, ensuring that the cell cycle progresses in a regulated manner.

For example, different cyclin-CDK complexes are involved in the G1 phase, S phase (where DNA is replicated), and the M phase (mitosis). The precise regulation by cyclins helps to prevent errors during cell division, which could lead to problems like cancer if the cycle is not carefully controlled. This activation and regulation process is essential for cellular function and life, making cyclins critical components of the cell cycle machinery.