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 and the regulatory mechanisms involved in controlling cell progression through the G1, S, and G2 phases. This quiz covers the key players such as cyclins, cyclin-dependent kinases, cyclin-binding proteins, and mitogens.