1. Chapter 8

2. Cells must divide for Growth Repair

3. Cells cannot just continue to grow larger for two reasons: Exchanging materials The surface area of the cell membrane must be large enough to support the volume of the cell. Otherwise, the cell struggles keeping up with the exchange rate of food, oxygen and water across the membrane. Information overload Too many demands on the DNA to get its information where it is needed.

4. Mitosis- The process by which a cell divides, forming two “daughter” cells These daughter cells are identical to the parent cell

5. Which cells ? Eukaryotic somatic (body) cells undergo mitosis Prokaryotic cells go through a process called binary fission

6. Chromosomes Made up of DNA wrapped tightly around histone proteins DNA + histones = chromatin fiber and looks like “beads on a string” During mitosis chromatin condenses and coils to form chromosomes

7. Chromosome: Sister chromatids- Each side of a duplicated chromosome Centromere- Center of a chromosome, holds sister chromatids together

8. Chromosome number varies for each species Humans= 46 Cat= 38 Fruit fly= 8

9. The cell cycle Mitosis is part of the cell’s life cycle This cycle includes the following stages: Interphase Mitosis Cytokinesis

10. Interphase The longest phase of the cell cycle The cell prepares to divide 3 phases, or checkpoints, in Interphase

11. Phases of Interphase G1 - intense cell growth, cells contents duplicated S - DNA is replicated (copied) G2 - more growth and final preparation for cell division G0- cell enters this phase when something is wrong and it either can’t or won’t divide. Ex: unstable environment, DNA was copied incorrectly, more cells not needed at that time

12. The Cell Cycle

13. After a cell goes through all the checkpoints, it is ready to divide! The Mitotic phase of the cell cycle includes Prophase Metaphase Anaphase Telophase

14. Prophase Nuclear envelope disappears Chromatin condenses Chromosomes are first visible Centrioles split and move to opposite sides of the cell

15. Prophase

17. Metaphase Chromosomes line up in the middle of the cell (equator) Spindle fibers connect to chromosomes at the centromere Metaphase = Middle

18. Metaphase

19. Metaphase (plant cell)

20. Anaphase Sister chromatids pulled apart to opposite sides Spindle fibers shorten Anaphase = Away, or Apart

21. Anaphase

23. Telophase Two sets of genetic information on either side of the cell Nuclear envelope reforms around each set Chromosomes no longer visible (unravel into chromatin again)

24. Telophase

25. After mitosis is complete, the cell has one thing left to do- split! (cytokinesis)

26. Cytokinesis Splitting of the cytoplasm Forms two new distinct “daughter” cells Two cells are genetically identical In animals- Cell membrane “pinches off” In plants- Cell plate forms

27. Cytokinesis In animals: Cell membrane “pinches off” In plants: Cell plate forms

28. Video links http://www.youtube.com/watch?v=VlN7K1-9QB0 http://www.youtube.com/watch?v=nPG6480RQo0 &feature=related http://www.youtube.com/watch?v=nPG6480RQo0 &feature=related

30. THE END