1. Regulating the Cell Cycle

2. How do cells know when to divide? - ◦Ex: Most muscle and nerve cells do not divide at all once they develop, and cells of the skin and digestive tract grow and divide rapidly throughout life.

3. Cyclins Discovered in early 1980’s -

4. Regulatory Proteins - ◦Allow the cell cycle to proceed only when certain events have occurred in the cell  Ex: Chromosomes have been replicated - ◦Respond to events outside the cell ◦Growth Factors – -  Important in embryonic development and wound healing

5. Kinases At some checkpoints, enzymes are produced to regulate reproduction Kinases: -

6. Cell Death Cells can end their life in 2 ways… 1. die by accident due to damage or injury 2. - *Chromatin shrinks and cell membrane breaks apart. * Key role in shaping tissues and organs

7. Checkpoint Failures - ◦The cell continues to divide Moles and tumors can form ◦-

8. Malignant Vs. Benign Not all tumors are Cancerous! -are noncancerous and do not spread to the surrounding healthy tissue. -are cancerous and invade and destroy surrounding tissue.

9. Cancer Cancer – - Cancer cells do not respond to the signals that regulate the growth of most cells! -

10. Characteristics of Cancer Cells 1) - ◦Controls are lost, reaching high densities, increase blood and capillary count 2) - ◦Missing proteins, shrunken cytoskeleton 3) - ◦Do not stay anchored to proper tissues, break away to other tissues and colonize

11. What causes cancer? - ◦They no longer respond to internal or external regulators. Sources of Defects: ◦Smoking or chewing tobacco ◦Radiation exposure ◦Other defective genes ◦Sometimes viral infections

12. Causes of Cancer

13. Gene p53 Scientists have found many cancer cells have a defect in a gene called p53. -

14. Treatments for Cancer Surgical removal Radiation therapy – - Chemotherapy – -