Why is CDK activity cyclic when CDK protein levels are roughly constant?
- A
CDK loses phosphates during S phase
- B
CDK is degraded each cycle
- C
CDK enters the nucleus only at metaphase
- Dcheck_circle
CDK requires binding to cyclin, whose levels rise and fall
Explanation
CDKs are present throughout the cycle but only active when bound to cyclins. Cyclic accumulation and destruction of cyclins drives the cyclic activity of CDKs.