Question

look back at the notes you took throughout the video. what determines when the cell should move on to the next cell cycle phase? rise and fall of various cdk levels. rise and fall of various cyclin levels. rise and fall of spindle fiber levels. rise and fall of dna concentration levels. rewatch

Explanation:

Cell cycle progression is controlled by cyclin-dependent kinases (CDKs), but CDK activity is directly regulated by the rise and fall of cyclin protein levels. Cyclins bind to CDKs to activate them, and different cyclin levels peak at specific cell cycle phases to trigger transitions. Spindle fibers, DNA concentration, and CDK levels alone do not determine phase timing; cyclin fluctuations drive the sequential phase changes.

Answer:

Rise and fall of various cyclin levels.