What is the function of Cyclin A during the cell cycle?

Cyclin A plays a crucial role during the cell cycle, specifically in the regulation of DNA replication. It acts by activating cyclin-dependent kinases (CDKs), particularly CDK2, which is essential for the transition from the G1 phase to the S phase. During the S phase of the cell cycle, Cyclin A-CDK2 complexes facilitate the initiation and progression of DNA replication, ensuring that the genetic material is accurately copied before the cell divides.

This activation is a key regulatory mechanism that ensures the cell is adequately prepared for mitosis, marking the importance of Cyclin A in maintaining the integrity of cell division. Hence, option C accurately describes the function of Cyclin A by highlighting its role in activating DNA replication.