1. Cell Cycle
Mitosis and Cancer

2. What is the cell cycle?
The cell cycle is the regular pattern of growth, DNA Replication, and cell division that occurs in eukaryotic cells.
The stages of the cell cycle gets their names from early studies of cell division.

3. Cell Cycle Stages Stages in growth & division Interphase G1 Phase
S Phase
G2 Phase
M Phase - Mitosis
Cytokinesis

4. Interphase – “Resting Phase”

5. G1 Phase (Gap 1) Cell carries out normal functions
Cell increases in size & organelles increase in numbers
A cell spends most of its time in the stage
Important checkpoint.

6. Synthesis (S) Phase Synthesis means to combine parts to make a whole.
Copying of all of DNA’s instructions
Chromosomes duplicated
Human cells – 46 chromosomes double to 92.

7. G2 Phase (Gap 2) Second growth stage
Time between DNA synthesis & mitosis
Cell continues growing
Needed proteins produced
Important checkpoint

8. M Phase - Mitosis The division of the cell nucleus and its contents.
Nuclear membrane dissolves, the duplication of DNA condenses around proteins and separates, and two new nuclei form.
Cell’s energy used to make 2 identical daughter cells
Stages
Prophase, Metaphase, Anaphase and Telophase

9. Chromosomes condense at the start of Mitosis.
A chromosome is one long continuous thread of DNA that consists of numerous genes along with regulatory information.
Each chromosome consists of two identical “sister” chromatids.
Each pair of chromatids is attached at an area called the centromere

10. Mitosis

11. Steps in Prophase DNA coils tightly & becomes visible as chromosomes
Nuclear membrane disappears
Nucleolus disappears
Centrioles migrate to poles
Spindle begins to form

13. Steps in Metaphase
Spindle fibers from centrioles attach to each chromosome
Cell preparing to separate its chromosomes
Cell aligns its chromosomes in the middle of the cell

14. Metaphase

15. Steps in Anaphase Cell chromosomes are separated
Spindle fibers shorten so chromosomes pulled to ends of cell

16. Anaphase

17. Steps in Telophase Separation of chromosomes completed
Cell Plate forms (plants)
Cleavage furrow forms(animals)
Nucleus & nucleolus reform
Chromosomes uncoil

18. Telophase
       Plant            
Animal

19. Cytokinesis Division of the cytoplasm Occurs after mitosis
Forms two, identical daughter cells

20. Cytokinesis
Cell Plate Forming in Plant Cells

22. How long does it take for cells to divide?
Cell Type
Time
Fly Embryo
8 minutes
Bacteria
20 minutes (Binary Fission)
Human Skin
20-24 hours
Human Nerve Cells
Never once matured
Human Liver
1 year
Onion Cells
12 Hours

23. Cancer

24. Cancer The common name for the mutation of the cell cycle.
Most cancer cell carry mutations, or DNA errors, in two genes that help make proteins involved in the cell cycle regulation.

25. DNA mutations disrupt the cell cycle.
Mutations may be caused by:
1. radiation
2. smoking
3. Pollutants
4. chemicals
5. viruses

26. While normal cells will stop dividing if there is a mutation in the DNA, cancer cells will continue to divide with mutation.

27. Due to DNA mutations, cancer cells ignore the chemical signals that start and stop the cell cycle.

28. Due to DNA mutations, cancer cells cannot communicate with neighboring cells. Cells continue to grow and form tumors.
Skin cancer

29. Treating Cancers
Cancer treatments include “chemo” drugs that can stop cancer cells from dividing. For example, Taxol is a natural plant product; it works by inhibiting the spindle fiber formation and disrupting mitosis. Basically, stopping these cancer cells from dividing. Some drugs can cause an adverse affect on the human body. Any rapidly dividing cell, like gastrointestinal tract, hair and bone marrow cells can be “killed’.

30. SUMMARY Normal Cell Division DNA is replicated properly.
2. Chemical signals start and stop the cell cycle.
3. Cells communicate with each other so they don’t become overcrowded.
Cancer Cells
Mutations occur in the DNA when it is replicated.
2. Chemical signals that start and stop the cell cycle are ignored.
3. Cells do not communicate with each other and tumors form.

31. Links http://www.youtube.com/watch?v=Hm03rCUO DqgpE
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