3 Questions
What is the purpose of the cyclin-dependent kinases (M and S)?
To phosphorylate the cyclin-binding proteins
What is the purpose of the cyclosome?
To target the cyclins for degradation
What will happen if there are no mitogens present?
The cell will enter the G0 phase
Study Notes
- 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.
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