1. IV. External & Internal Controls of Cell Division

2. Density Dependent Inhibition Crowding inhibits cell division  why Anchorage dependence  why Conclusion – 2 reasons cell division is halted

3. Introduction Different cells divide at different times and rates:  Human skin cells  Liver cells  Muscle & nerve cells

4. Evidence from Cell Culture Studies & Growth Factors Figure 12.18  Method – allowed identification of growth factor PDGF

5. Restriction Point (G o ) What and when Result Examples  Most cells  Liver  Nerve

6. VII. Cyclical Changes in Regulatory Proteins Function as a Mitotic Clock Figure 12.17

7. Introduction Controls exist  Reason

8. Control Mechanism by interactions of protein kinases & cyclins Terms:  Protein kinases Definition Action  Cyclins Definition Function  MPF (maturation Promoting Factor) Definition Composition

9. Five Steps in Control Process

10. VIII. Cancer Cells & Cell Division Don’t respond to controls – 3 ways Characteristics  Not affected by  Can stop  Are immortal – HeLa Cells

11. Consequences of loss of normal controls Tumor formation  Types Benign Malignant  Can metastasize Definition Reason Metastasis