1. Cellular Division: Mitosis (Text Ch. 10, pp. 240-248)

2. Reasons for Cell division  Basis of reproduction for all cellular organisms  Enables multicellular organisms to grow  Replaces worn-out or damaged cells and tissue

3. “Analysing Data”, p. 249  Life Span of Human Cells –1. White blood cells: function vs lifespan –2. Consequences of injury to heart + spinal cord? Smooth muscle? –3. Hypothesis for data –4. Cancer: predict data table

4. Summary of Cell division  Prior to division, cell replicates all of its DNA –One complete copy will go to each “daughter” cell

5. Recall:  genetic info for eukaryotic cells is contained in a membrane-bound nucleus  Before the cell can divide, the nucleus must also divide

6. Recall:  Two types of cell division: –1. Mitotic  46 double  46 single chromosomes  Asexual, body cells –2. Meiotic  46 double  23 single chromosomes  Sexual cells

7. Two Main Stages of Cell Division  1. Mitosis: –division of the nucleus –forms 2 daughter nuclei –each has a full, identical chromosome set  2. Cytokinesis: –division of the cytoplasm b/w 2 daughter cells

8. Cell Cycle  Interphase ~ 90% of time  Mitotic phase ~10% of time

9. Nucleus contains DNA and proteins  DNA packed tightly into chromatin fibres  Chromatin: – DNA coiled around histone molecules (protein) –Coils are then coiled into long fibres  Fibres dispersed throughout nucleus

10. Chromosome Structure Fig. 12-10, p. 297

11. Chromosome Formation during Mitosis  Chromatin fibres gather + coil  Bunched into compact chromosomes  Set # of chromosomes per sp.

12. Interphase  Cell growth (G1)  DNA synthesis (S) –Chromosomes duplicate, still loosely packed  Produces proteins + organelles for div. (G2)

13. Prophase  Chromatin fibres condense into chromosomes –two “sister” chromatids –attached at a narrow waist (centromere)  Spindles form

14. Prophase, cont’d  Centrioles at poles  Spindles grow, reach chromosomes  Nuclear envelope breaks down & disappears

15. Metaphase  Chromosomes line up along metaphase plate at centre  Each chromatid connected at centromere to a spindle fibre from each pole

16. Anaphase  Centromeres split as spindle fibres pull chromatids apart  Form group of single chromosomes at each pole  Cell elongation begins

17. Telophase  Cells elongate  Daughter nuclei appear at each pole as envelope re-forms  Chromatin fibres uncoil

18. Telophase and Cytokinesis  Cleavage furrow (animal) –Cell plate (plant)  Cells contain ½ the cytoplasm, but same # chromosomes as parent cell

19. Mitosis in action:  http://www.teachersdomain.org/reso urce/tdc02.sci.life.stru.dnadivide/ http://www.teachersdomain.org/reso urce/tdc02.sci.life.stru.dnadivide/ http://www.teachersdomain.org/reso urce/tdc02.sci.life.stru.dnadivide/  “Go Online” (p. 245 text)

20. Controls on Cell Division  Cell activity controlled by proteins (e.g. cyclins) and other regulators –E.g. healing a cut  What might happen without controls? –E.g. Cancer – how does it work? –http://www.youtube.com/watch?v=dK9 UcjSPkLs&feature=related http://www.youtube.com/watch?v=dK9 UcjSPkLs&feature=relatedhttp://www.youtube.com/watch?v=dK9 UcjSPkLs&feature=related