1. Why do cells Divide?
What did we discover in the cell size lab? How does your body prepare a wound? How do you replace all of the skin cells you loose every day? What happens when Cell division doesn’t happen correctly?

2. Mitosis! When it happens correctly Life is great!
When Mitosis goes wrong (Cancer)

3. Define the following:
Chromosome, Sister Chromatid, Centromere, Cell Cycle. Centriole

4. What is Cell Division?
Cell Division is the process of making two identical daughter cells from one parent cell
Each cell has complete DNA & organelles
Human Cell Division:
A Chromosome = a little packet of DNA.
You have 46 little packets in each cell 46
46 chromosomes 46

5. Why do Cells Divide?
Cells divide because the smaller the cell, the more efficient the transport of necessary molecules into and out of them
The greater the surface area to volume ratio, the better
The faster oxygen diffuses into your cells, the more ATP you make!

6. When do Cells Divide? Cells divide when an organism: Needs to grow
Needs to repair itself
Needs to reproduce (prokaryotes only!)

7. Who does Cell Division? All organisms!
Single celled (prokaryotes) or multi-cellular (eukaryotes)

8. How does Cell Division Happen?
Cell Division occurs in a series of predictable phases:
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
The term “Mitosis” refers to prophase through telophase

9. During Interphase
Growth occurs… DNA Replicates… DNA is in the form of chromatin

10. Mitosis: Prophase
92 Chromosomes condense and pair up into sister chromatids
Centrioles go to opposite sides of cell and spindle forms
Nuclear envelope breaks down
Chromosomes become attached to spindle

11. Mitosis: Prophase

12. Mitosis: Metaphase
46 pairs of chromosomes line up across the center of the cell
Spindle completely attaches to the centromere, a protein at the center of the chromosomes

13. Mitosis: Anaphase
Sister chromatid pairs are pulled apart by spindle fibers
Each side of the cell now has 46 chromosomes

14. Mitosis: Telophase Chromosomes become uncondensed
Nuclear envelope reforms
Spindle breaks apart

15. Cytokinesis
In animal cells, cells are pinched off to form two cells (like a drawstring)
In plant cells, a cell plate forms between the two cells, eventually becoming a wall

16. Quiz…. You must show understanding of the process of cell division
You and your partner must show one cell creating two cells and illustrate:
Interphase,Prophase,Metaphase,Anaphase, Telophase
ase and cytokinesis by making chalk drawings!
Drawing must show

17. Must show 1 cell becoming 2 and illustrate important components in each stage:
Chromatin
Chromosomes (relative # and location)
Centrioles
Spindle fiber
Centromeres
Nuclear Membrane (dissapearing and forming)
Cell Membrane

18. Regulating Cell Division
How do cells know when it is time to divide?

19. Internal Regulators
Each phase (G1, S, G2) in the cell cycle has a “checkpoint” at the end
Cells cannot continue to the next phase unless requirements are met
‘Stop’ and ‘Go’ signals are given by proteins called cyclins
Q: What is the major requirement to go from S phase to G2?

20. Regulation Gone Wrong: Cancer
Cancer Cells do not respond to regulators (growth factor, space, attachment, checkpoints)
Cancer cells can be immortal, and form a tumor

21. Cancer Basics
In benign tumors, the abnormal cells stay at the original site
Benign tumors are often not harmful
Malignant tumors impair the function of organs
Malignant tumors can detach and spread throughout the body (metastasis)
“Cancer” is malignant

22. Who Gets Cancer? Your risk for cancer is determined by:
Genes
Lifestyle
Environment
Genes: DNA can contain sections that are irregular and prone to cause inappropriate cell division
Cancer early in life can suggest a genetic cause

23. Who Gets Cancer?
Lifestyle: tanning, smoking, drinking, unprotected sex can all raise risk for cancer
Environment: pollutants in air and water (particles, radiation, etc.) can be inhaled/ingested and cause cancer

24. What you need to do… Show that you understand how cells divide
Show your understanding of the important components of a cell:
Centromeres/Centrioles (M and M’s)
spindlefibers (String)
Chromosomes /Chromotin (Licorice)
Nuclear Membrane (String)
You must show understanding in: Interphase , All phases of Mitosis, and
cytokenisis THIS IS ALL OR NOTHING!!!!