Question

The cell-cycle control system uses Cdk inhibitory proteins:

(a). to induce cyclin gene expression.
(b). to degrade Cdks.
(c). to degrade cyclins.
(d). to arrest the cell cycle at specific checkpoints.

Answer 1

Cdk inhibitory proteins are used to arrest the cell cycle at specific checkpoints, ensuring progression only once proper conditions are met.

Step-by-step explanation:

The cell-cycle control system uses Cdk inhibitory proteins to arrest the cell cycle at specific checkpoints. These inhibitors ensure that the cell cycle does not proceed until certain conditions are met, effectively acting as a form of quality control. Cyclin-dependent kinases (Cdks) require the binding of cyclins to form active complexes that facilitate the cell cycle progression. However, the levels of cyclins fluctuate, and without the proper concentration of fully activated cyclin/Cdk complexes, the cell cycle cannot advance through checkpoints. Therefore, the correct answer to the student's question is (d) to arrest the cell cycle at specific checkpoints.