What is the role of cyclins in cell cycle regulation?

Cyclins play a crucial role in the regulation of the cell cycle primarily by activating cyclin-dependent kinases (Cdks). In the context of cell cycle progression, cyclins function as regulatory proteins whose levels fluctuate throughout the cell cycle. When cyclins bind to their partner Cdks, they induce a conformational change that activates the kinases. These activated Cdks then phosphorylate specific target proteins, leading to the progression of the cell cycle through its various phases (G1, S, G2, and M).

This process is essential for the proper and timely transition between different phases of the cell cycle, ensuring that cells accurately replicate their DNA and divide. Without the activation of Cdks by cyclins, the cell cycle would be unable to proceed effectively, which could lead to errors in cell division and potential consequences such as cancer. Therefore, the correct answer highlights the critical function of cyclins in cell cycle regulation through the activation of Cdks.