The cell-cycle control system uses Cdk inhibitory proteins to do what?

Cdk inhibitory proteins play a crucial role in regulating the cell cycle by halting its progression at specific checkpoints. These proteins bind to cyclin-dependent kinases (Cdks) and inhibit their activity, effectively pausing the cell cycle to allow for repair of damaged DNA or other cellular processes that must be completed before the cell can proceed. This regulation is essential to maintaining genomic integrity and preventing the propagation of cells with damaged or incomplete genetic information. By ensuring that the cell does not progress to the next phase until conditions are appropriate, Cdk inhibitory proteins help safeguard against potential errors that could lead to malfunctioning or cancerous cells.

In contrast, other options do not align with the specific function of Cdk inhibitory proteins. Degrading cyclins or Cdks is not within the functional scope of these inhibitors; rather, these processes involve different mechanisms of cell cycle regulation. Triggering different phases of the cell cycle is primarily carried out by the activation of Cdks rather than their inhibition. Thus, the correct focus on arresting the cell cycle at key transition points underscores the important regulatory role of Cdk inhibitory proteins.