Final answer:
The degradation of cyclin results in the inactivation of Cdk, preventing the Cdk/cyclin complex from forming and thus stopping the cell from advancing through the cell cycle.
Step-by-step explanation:
The degradation of cyclin leads to the inactivation of Cdk (cyclin-dependent kinases). Cyclins are necessary for the activation and regulation of Cdks, which are crucial for advancing the cell cycle.
The cyclin levels fluctuate throughout the cycle and when bound with Cdk form a complex that must also be phosphorylated to become fully active. This phosphorylation changes the shape of the Cdk, activating it so it can then phosphorylate other proteins. When cyclin is degraded, this prevents the formation of the Cdk/cyclin complex, and as a result, Cdk is inactivated and cannot move the cell past specific checkpoints in the cell cycle.