What are mitogens, and what role do they play in the G1 phase?

• A. Mitogens are enzymes that directly replicate DNA.
• B. Mitogens are checkpoints that halt the cell cycle.
• C. Mitogens are signals that stimulate cell growth by activating cyclins and cyclin-dependent kinases.
• D. Mitogens are proteins that repair DNA damage.

Answer: (C)