Cell Cycle Checkpoints and Regulation Quiz

• The cell cycle is stopped at the third checkpoint when chromatids are attached to the poles correctly.
• This checkpoint is regulated by cyclin degradation.
• The cyclin degradation pathway is activated by the cyclin-dependent kinases (M and S).
• The cyclin-dependent kinases in turn phosphorylate the cyclin-binding proteins (CBP), which then activate the cyclosome.
• The cyclosome then targets the cyclins for degradation.
• The cell can enter the G1 phase if there are no mitogens present, but will eventually enter the S phase if mitogens are present.
• The G1 phase is regulated by the cyclin-dependent kinases, and the cell will eventually enter the G0 phase if no mitogens are present.
• The cell can be held in the G1 phase by the cyclin-dependent kinases, and will eventually enter the G2 phase if mitogens are present.

Test your knowledge of the cell cycle checkpoints, including the role of cyclin-dependent kinases, cyclins, and the regulation of phases such as G1, S, and G2. Explore how mitogens influence the progression through the cell cycle.