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 (G1) 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 (G2) 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 G1 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