1. Chapter 10 http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/Cell_cycle.html Section 3: Regulating the Cell Cycle

2. Objectives Identify a factor that can stop cells from growing. Describe how the cell cycle is regulated. Explain how cancer cells are different from other cells.

3. Cell Growth and division in multicellular organisms are carefully controlled.

4. Controls on Cell Division Scientists can study cell growth by placing cells in a petri dish containing nutrient broth. Cells will grow until they have formed a thin layer on the dish. Cells will stop growing when they come in contact with each other.

5. Cell Cycle Regulators Timing of the cell cycle in Eukaryotic cells is regulated by a family of proteins called cyclins. More recently, dozens of proteins have been discovered that help regulate the cell cycle.

6. 2 Types of Regulators 1.Internal Regulators -allow cell cycle to proceed when certain processes have happened. *All Chromosomes have replicated. *All chromosomes have attached to spindles.

7. 2. External Regulators -Signals outside of cell that stimulate cell cycle to speed up or slow down. *Example: Growth Factors—stimulate growth and division of cells.

8. Uncontrolled Cell Growth Sometimes cells lose the ability to control cell growth. Cancer cells do not respond to the signals that regulate the growth of most cells.

9. Causes: –Tobacco –Radiation exposure –Viral infection *Cancer can result from a defect in the p53 gene which controls parts of the cell cycle.

10. 10-3 Review 1.What are cyclins? 2.List and describe the two types of cell cycle regulators. 3.How do cancer cells compare to normal cells? 4.Name two factors that can cause cancer. 5.What gene can be mutated, resulting in loss of control over parts of the cell cycle?