1. 10.3 Regulating the Cell Cycle

2. 2 Which of the cells depicted in the line graph below are most likely cancerous?

3. II. Control of Cell Cycle A. How do cells know when to divide? 1. Cells have proteins called cyclins that regulate timing of cell cycle B. Cell Cycle Regulators: 1. Internal Regulators a. Correct # of chromosomes b. Spindle fibers are attached to all chromosomes (phase?) 2. External Regulators a. cut that needs healing b. neighbors C. Cell cycle has checkpoints at which protein signals can: 1. Trigger the next phase, or 2. Delay next phase 3. Stop division (the most important checkpoint, G 1 )

4. Cancer: When control is lost Cancer a. Uncontrolled cell growth b. Disorder of cell division c. Cells keep on dividing, creating tumors d. Due to mutations in genes e. Causes of mutations can be chemicals, radiation & viruses f. Most cancers require many mutations before they begin