During which stage of the cell cycle do CDKs primarily act?

Cyclin-dependent kinases (CDKs) play a crucial role in regulating the cell cycle, functioning primarily during all phases of the cell cycle by facilitating progression and transition between distinct phases. CDKs are activated upon binding to cyclins, which are proteins that vary in concentration throughout the cycle.

During the G1 phase, CDKs promote the cell’s transition to the S phase by phosphorylating target proteins that drive cell growth and DNA synthesis. In the S phase, CDKs are integral in DNA replication by ensuring that the necessary proteins are activated for this process to occur efficiently. Additionally, during the G2 phase, CDKs help prepare the cell for mitosis by facilitating processes like DNA repair and chromosome condensation. Even in the M phase, CDKs are involved in the progression of mitosis, ensuring that cell division occurs seamlessly.

Thus, the action of CDKs is not restricted to a single phase; rather, they are essential regulators acting throughout the entire cell cycle, making the correct perspective that they operate during all phases.