Regulation of the Cell Cycle Chapter 5 Section
- Slides: 12
Regulation of the Cell Cycle Chapter 5 Section 3
The Cell Cycle is Carefully Controlled • The cell cycle has key checkpoints (inspection points) at which feedback signals from the cell can trigger the next stage of the cell cycle (green light). • The cell cycle in eukaryotes is controlled by many proteins.
The Cell Cycle is Carefully Controlled • Cell growth (G 1) checkpoint - this check point makes the key decision of whether the cell will divide. - if conditions are favorable, certain proteins will stimulate the cell to begin the synthesis (S) phase.
The Cell Cycle is Carefully Controlled • DNA synthesis (G 2) checkpoint - DNA replication is checked at this point by DNA repair enzymes. - if this checkpoint is passed, proteins help trigger mitosis.
The Cell Cycle is Carefully Controlled • Mitosis checkpoint - triggers the exit from mitosis - signals the beginning of the G 1 stage.
When Control is Lost: Cancer • Genes contain the information necessary to make the proteins that regulate cell growth and division. • If a gene is mutated, the protein may not function, and regulation of cell growth and division can be disrupted.
When Control is Lost: Cancer • Cancer: the uncontrolled growth of abnormal cells. - over-production of growth-promoting molecules, speeding up the cell cycle. - inactivating the proteins that slow or stop the cell cycle.
When Control is Lost: Cancer • Mutations can occur spontaneously or as a result of environmental factors. • Risk factors: - tobacco - exposure to ultraviolet radiation