Final answer:
The cell-cycle control system can halt the cycle primarily through the inhibition of cyclin-dependent kinases (Cdks) and cyclins. These inhibitory mechanisms involve Cdk inhibitors which maintain a block on Cdks until specific cell-cycle events are completed.
Step-by-step explanation:
The cell-cycle control system uses a variety of methods for regulation, which involves both the activation and inhibition of key proteins involved in the cycle. Specifically, when considering how the cycle can be halted, the most relevant method is the inhibition of cyclin-dependent kinases (Cdks) and sometimes the inhibition of cyclins. These inhibitory mechanisms essentially block the progression of the cell cycle until certain conditions are met or issues are resolved. This is achieved through the action of molecules known as Cdk inhibitors, which prevent the full activation of Cdks and ensure the cell cycle does not proceed past checkpoints prematurely.
These inhibitor molecules monitor the specific events occurring in the cell cycle, and the block they introduce is maintained until the cell resolves any problematic conditions that could impede a healthy cell cycle progression.