Final answer:
In order for cells to divide, a cue for division is provided by growth factors, cyclin-dependent kinases (Cdks), and cyclins. Tumor suppressor genes act as negative regulators in the cell cycle.
Step-by-step explanation:
In order for cells to divide, a cue for division is needed. This cue is provided by growth factors, which are proteins that arrive at the cell's plasma membrane and trigger the cell to begin dividing. Additionally, cyclin-dependent kinases (Cdks) and cyclins, which are internal molecular signals, regulate cell transitions through the checkpoints in the cell cycle. They allow the cell cycle to advance to the next stage. Tumor suppressor genes, on the other hand, act as negative regulators by monitoring cellular conditions and halting the cell cycle until specific requirements are met.