A cell's progression through the cell cycle requires the activity of several cyclin-dependent kinases. What are these cdks, how are they activated, how are they inactivated, when do you see their levels rise and what are their targets?

Answer: 1. Cyclin-dependent kinases.

2. The activation process is in two steps: binding of cyclin to cdk and then phosphorylation of cdk cyclin.

3. They are activated when cdks sends signals to cell that is pass already into the next stage of the cell cycle.

4. They are inactivated by the combination of P21 and Thr-14/Tyr-15 phosphorylation after uv induced DNA damage.

5. Changes are seen in target protein level when cdks level rises.

6. The targets are protein that promotes cell divisions.