2. The Cell Cycle…Gone Wrong How do cells know when to divide… What controls the cell cycle… Cells grown in a lab will continue to divide until they come in contact with other cells If you scrape away some cells, they will start dividing again… Most of the time, cells know what to do and how to do it But how…

3. 10.3 Regulating the Cell Cycle Cyclins – a family of proteins that help regulate the cell cycle Internal regulatory proteins – proteins inside a cell – Make sure everything is timed properly – Cells don’t enter mitosis until AFTER DNA is replicated External regulatory proteins – respond to events outside a cell – Heal wounds; tell cells when to stop dividing – What if cells kept going and going and going…

4. Cell Death  Cells are “born” in the cell cycle, and therefore must “die” Happen by accident or injury, or… Programmed to die = Apoptosis Apoptosis is like self-destruction mode Cell and DNA shrinks, parts break off, and neighboring cells clean up the remains Key role in embryonic development

5. Uncontrolled Cell Growth If cells grow out of control, cancer results Cancer – inability to control cell growth Cancer cells do not respond to signals that regulate most cells, and will divide out of control A mass of cancerous cells = Tumor Benign tumors – do not spread Malignant tumors – spread through body

6. What causes cancer? Gene defects that regulate cell growth and division – Defect of gene called p53 is most common Smoking or chewing tobacco Radiation exposure (X rays, UV rays) Even viral infection Common factor = can’t control cell cycle

7. Treatments for Cancer Removal Radiation – target a specific area of the body Chemotherapy – chemical compound that kills cancer cells (it targets cells that grow rapidly, so it kills healthy cells sometimes too) – Serious side effects

8. In which phase does the nuclear envelope break down?

9. In which phase do chromosomes line up at the middle?

10. In which phase is DNA replicated?

11. In which phase are chomatids pulled apart?

12. In which phase does the nuclear envelope reform?

13. What is the final product?

14. During the videos, consider… How is the cell cycle different in plants compared to animal cells? How does cell division benefit us? How can the cell cycle cause us harm?

15. What is cancer, exactly? Cancer is what occurs when the cell cycle gets out of control and cells don’t die when they’re supposed to What causes cancer? Can we cure cancer?

16. http://www.youtube.com/watch?v=3kpR5RSJ 7SA http://www.youtube.com/watch?v=3kpR5RSJ 7SA Does your cell cycle drawing match these descriptions? http://www.youtube.com/watch?v=Q9cuEYSt 0GE&feature=related http://www.youtube.com/watch?v=Q9cuEYSt 0GE&feature=related