4.6.1 Cell cycle progression requires successful passage through multiple checkpoints

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Checkpoints:

  1. G1, the most important: Is the cell big enough? Is there the protein required?
  2. G2: Is the DNA well synthesized?
  3. M: Are the spindles well functioning?

If any of these checkpoints are problematic, there will not be a signaling engaging it to go on dividing and the cell enters the $G_0$ phase, where cell cycle is stopped

4.6.2 Interactions between cycling & cyclin-dependent kinases control the cell cycle

Cyclin activates CDK and form a Cyclin-CDK complex named MPF(Maturation promoting factor), which triggers a cell’s passage to past the G2 checkpoint into M-phase by phosphorylating target protein

CDK concentration is constant, but Cyclin concentration is not

Cyclin concentration increases as cell during interphase

External control: Platelet Derived Growth Factor (PDGE): when the cell is normal, it grows normally; however, when PDGE occurs, cells will squeeze each other to grow

4.6.3 Disruption of cell cycle checkpoints → Death & Cancer

DNA damage →apoptosis

mutation in p53 gene → cancer

Oncogenes and Tumor Suppressor Genes