2. CELL GROWTH AND DIVISION: THE CELL CYCLE

3. Importance of Cell Division Growth of organism (adding more cells) To replace dead or damaged cells (healing)

4. Why do cells need to divide? When cells get too large: They can’t get nutrients fast enough They can’t get rid of wastes fast enough The nucleus can’t keep up with the demands of the cell

5. Coiled DNA and protein (has instructions for the cell to divide) Chromatids - identical copies of information (sister chromatids) Centromere - place where chromatids attach Chromosomes

6. TYPICAL CELL DIVISION (MITOSIS) 1 CELL 2 IDENTICAL Daughter CELLS Each cell has the same # of chromosomes 46 *Humans have 46 chromosomes in each cell (except sperm and egg)

7. THE CELL CYCLE Interphase, Mitosis and Cytokinesis

8. CELLDIVISIONCELLDIVISION

9. Interphase G1 phase - cell grows in size S phase - cell duplicates its chromosomes (DNA replication) G2 phase - cell makes more proteins to help prepare for cell division

10. Mitosis Divided into 4 phases: Prophase Metaphase Anaphase Telophase

11. Prophase Nuclear membrane breaks down Spindle fibers begin to form Centrioles (organelle involved in cell division) move apart Chromatin coils into chromosomes (become visible)

12. Metaphase Chromosomes migrate to the middle of the cell Spindle fibers are attached to the centromeres

13. Anaphase Sister chromatids pull apart and move to opposite ends of the cell

14. Telophase New nucleus forms around each set of chromosomes Cell pinches inward at center Chromosomes unwind into chromatin Spindle fibers break down

15. Cytokinesis (after mitosis) Division of the cytoplasm (cell divides in two - begins during Telophase) Plant cells - cell plate forms (new cell wall) Animal cells - cleavage furrow forms

16. How is the cell cycle controlled? Enzymes and other proteins determine: When a cell should start dividing When a cell should stop dividing *when these proteins don’t work right or are not made correctly, cancer can result

17. CANCER A disease that results from mutations (mistakes) in a cell’s DNA which results in the uncontrolled division of cells Tumor - mass of abnormal cells resulting from rapid cell division

18. Types of Tumors Benign - mass of abnormal cells which is not cancerous Malignant - mass of cancerous cells that invade nearby tissues and spread throughout the body

19. What do cancer cells do in the body? They starve nearby cells by causing blood vessels to grow into the tumor to supply it with nutrients (angiogenesis) They can metastasize (spread) to the bloodstream and go to other areas of the body and grow new tumors See animation