1. Multicellular organisms depend on cell division for: – Development from a fertilized cell – Growth – Repair

2. Fig. 12-2 100 µm200 µm 20 µm (a) Reproduction (b) Growth and development (c) Tissue renewal

3. Concept 12.1: Cell division results in genetically identical daughter cells Most cell division results in daughter cells with identical genetic information, DNA Somatic cells (body cells -nonreproductive cells) have two sets of chromosomes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

4. Fig. 12-3 20 µm

5. Eukaryotic cell division consists of: Interphase, stage prior to mitosis, cell growth Mitosis, the division of the nucleus Cytokinesis, the division of the cytoplasm Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

6. Interphase (about 90% of the cell cycle) can be divided into subphases: – G 1 phase (“first gap”) – cell growth – S phase (“synthesis”)- DNA replicates – G 2 phase (“second gap”)- cell growth The cell grows during all three phases, but chromosomes are duplicated only during the S phase Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

7. Fig. 12-5 S (DNA synthesis) MITOTIC (M) PHASE Mitosis Cytokinesis G1G1 G2G2

8. Mitosis is conventionally divided into four (five) phases: – Prophase – (Prometaphase) – Metaphase – Anaphase – Telophase Cytokinesis is well underway by late telophase BioFlix: Mitosis BioFlix: Mitosis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

9. Prophase Chromosomes are visible form sisters Nucleus and nucleolus disappears Centrosomes/ Centrioles appear, spindles form from centrosome

10. Fig. 12-10a Nucleus Prophase 1 Nucleolus Chromatin condensing

11. Metaphase Movement of centrosomes to the poles Movement of spindle fibers to reach the chromatids Movement of chromatids to the equator

12. Fig. 12-10c Metaphase 3

13. Anaphase Spindle fibers attach to kinetochores on the sisters chromatids Sister chromatids are pulled apart Chromosomes move as equal sets to the poles

14. Fig. 12-10d Anaphase 4

15. Telophase Nuclear membrane and nucleolus reappear Spindles/centrosomes disappear Cytokinesis occurs

16. Fig. 12-10e Telophase 5 Cell plate 10 µm

17. Cytokinesis: A Closer Look Cyto – cytoplasmic area separated In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow made from microfilaments In plant cells, a cell plate forms during cytokinesis made from the golgi vesicles forms a cell wall Animation: Cytokinesis Animation: Cytokinesis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

18. Video: Sea Urchin (Time Lapse) Video: Sea Urchin (Time Lapse) Video: Animal Mitosis Video: Animal Mitosis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

19. Cleavage furrow Fig. 12-9a 100 µm Daughter cells (a) Cleavage of an animal cell (SEM) Contractile ring of microfilaments

20. Fig. 12-9b Daughter cells (b) Cell plate formation in a plant cell (TEM) Vesicles forming cell plate Wall of parent cell New cell wallCell plate 1 µm

21. Fig. 12-10 Chromatin condensing Metaphase AnaphaseTelophase Prometaphase Nucleus Prophase 1 2 3 5 4 Nucleolus Chromosomes Cell plate 10 µm

22. Cell Growth Limits surface area / volume = ratio Lab we did showed as volume of a cell increase the ratio decrease Therefore there is a need to increase protein production to build more membranes for transportation of compounds around the cell

23. Rate of cell growth Bacteria replicate every ? Heart and nerve cells divide ? Skin and Digestive cells ?

24. Cells depend on ….. Another example of external signals is density- dependent inhibition, in which crowded cells stop dividing Most animal cells also exhibit anchorage dependence, in which they must be attached to a substratum in order to divide Growth factors nutrients that help cells through the cell cycle Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

25. Fig. 12-19 Anchorage dependence Density-dependent inhibition (a) Normal mammalian cells (b) Cancer cells 25 µm

26. Cancer cells exhibit neither density-dependent inhibition, anchorage dependence or a need for growth factors Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

27. Loss of Cell Cycle Controls in Cancer Cells Cancer cells do not respond normally to the body’s control mechanisms Cancer cells may not need growth factors to grow and divide: – They may make their own growth factor – They may convey a growth factor’s signal without the presence of the growth factor – They may have an abnormal cell cycle control system Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

28. Cancer cells form tumors, masses of abnormal cells within otherwise normal tissue If abnormal cells remain at the original site, the lump is called a benign tumor Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form secondary tumors Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

29. Cancer spreads Most commonly by the lymphatic system Local invasion Blood stream

30. Fig. 12-UN2

31. Fig. 12-UN3

32. Fig. 12-UN5