1. Chapter 12: The Cell Cycle
The student is responsible for:
All bold faced words in the chapter.
Being able to describe the stages of mitosis, Figure 12.5.
Lectures will emphasize “The Regulation of the Cell Cycle” pgs 224 – 229.

2. Figure 12.1a The functions of cell division: Reproduction
Reproduction of an amoeba
Cell division can have as its sole purpose to make a new individual.

3. Figure 12.1c The functions of cell division: Tissue renewal
Reproduction of bone marrow cells.
These bone cells are involved in replenishing blood cells: RENEWAL AND REPAIR.

4. Figure 12.2 Eukaryotic chromosomes
Kangaroo rat cells
During cell division, the fidelity or precision of DNA reproduction is amazing.

5. Figure 12.3 Chromosome duplication and distribution during mitosis
Chromatin: DNA and associated proteins in a thin state
Chromosomes: densely coiled DNA and the associated proteins
A duplicated chromosome is made of two sister chromatids attached at the centromere

6. Organelles and proteins are made
Figure The cell cycle
Organelles and proteins are made
Organelles and proteins are made
Cell Cycle:
The mitotic portion of the cell cycle is a small portion of the entire cycle
M phase consists of mitosis and cytokinesis
Interphase: consists of G1, S and G2 phases.

7. Figure 12.5 The stages of mitotic cell division in an animal cell: G2 phase; prophase; prometaphase

8. Figure The stages of mitotic cell division in an animal cell: metaphase; anaphase; telophase and cytokinesis.

9. Figure 12.5x Mitosis

10. Figure 12.6 The mitotic spindle at metaphase

11. Mitotic Spindle and Its Relationship to Chromosomes
Mitotic spindle is composed of microtubules
MTs emerge from the centrosome
The centrosome is an organelle but has no membrane
Centrosome replicates at the beginning of mitosis and each will end at one of the poles of the nucleus.
Spindle attaches at the kinetochore, a region on the sister chromatids.
Spindles from both ends of the nucleus attach to the kinetochores on each sister chromatid and through pulling and tugging align the chromosomes in the middle or metaphase plate

12. Are they shortening near the centrosome or the kinetochore?
Figure Testing a hypothesis for chromosome migration during anaphase
In order to move the chromosomes to the poles, the kinetochores need to shorten.
Are they shortening near the centrosome or the kinetochore?
After the microtubules were labeled with a laser, it was found that the MTs nearest the chromosome or kinetochore shortened.

13. Figure 12.8 Cytokinesis in animal and plant cells
Animal cell: There is a contractile ring of actin and myosin that pinches the cell.
Plant Cells: vesicles from the Golgi bodies move to the middle of the cell and produce a cell plate which becomes the new cell wall.

14. Figure 12.9 Mitosis in a plant cell

15. Figure 12-09x Mitosis in an onion root

16. Figure Mitosis

17. Figure 12.10 Bacterial cell division (binary fission) (Layer 3)

18. Regulation of the Cell Cycle
A molecular control system drives the cell cycle
Specific chemical signals in the cytoplasm regulation the cell cycle.
This was shown by fusing cells in different stages of the cell cycle and the cell not as advanced moved into the more advanced stage as if something from the cytoplasm of the advanced cell caused a stimulation.
This was called a Cell Cycle Control System

19. Regulation of the Cell Cycle cont’d
Cell Cycle Checkpoints
“Go” Checkpoints: is there enough protein, organelles, etc.
G1 Checkpoint
Most important in mammalian cells
Once past the G1 checkpoint, cell will complete the cell cycle
With no “go” signal, it remains in a nondividing state.
Some cells, liver cells, can transition from nondividing to dividing .
Other cells, muscle or nerve cells, remain in nondividing state.

20. Figure 12.13 Mechanical analogy for the cell cycle control system

21. Regulation of the Cell Cycle cont’d
The Cell Cycle Clock: Cyclins and Cyclin-Dependent Kinases
Kinases will phosphorylate proteins which can either activate them or inactivate them.
Kinase + cyclin is an active kinase so it is a cyclin-dependent kinase or CdK.
M Phase Promoting Factor or MPF is a complex of a kinase and cyclin.
MPF triggers movement of the cell cycle out of G2 and into mitosis
MPF will cause the phosphorylation of many proteins and these phosphorylated proteins can activate cellular processes. i.e., breakdown of the nuclear membrane.
MPF decomposes and inactivates itself.

22. Figure 12.14 Molecular control of the cell cycle at the G2 checkpoint

23. Internal and External Cues
Internal Signals: Messages from the Kinetochores
Anaphase is delayed until all the chromosomes are lined up properly and attached to the kinetochores.
If all the kinetochores are not attached to the microtubules then cell will not go into anaphase.

24. Internal and External Cues (cont’d)
External Signals: Growth Factors
Platelet Derived Growth Factor or PDGF
Platelets in the blood stream have receptors for this growth factor and when the receptors are bound to the PDGF, cell division is stimulated.
This happens in petri dishes as well as within your body.
Density-Dependent Inhibition
Anchorage dependence

25. Cancer Cells have escaped controls of the cell cycle
Tumor
Benign Tumor: if abnormal cells remain in original site.
Malignant Tumor
Metastasis

26. Figure 12.15 The effect of a growth factor on cell division

27. Figure 12.15x Fibroblast growth

28. Figure 12.16 Density-dependent inhibition of cell division

29. Figure 12.17 The growth and metastasis of a malignant breast tumor