What are the molecules that govern the transition from: place you answers next to each phase G1 S G2

cells use checkpoints at the end of G1 phase, end of G2 phase, and move through the cell cycle, do they breeze through from one phase to the next. The spindle checkpoint, at the transition from metaphase to anaphase. The general answer is that internal and external cues trigger signaling.

correct answer is a. and d.