1. Mitosis: Cell Division

2. Why do cells divide?
Growth
Repair
Replace dead cells

3. What cells divide often?
Skin
Stomach lining
Red Blood cells
Embryo
Plant roots
Hair
Nails

4. What cells rarely/never divide?
Nervous System
Liver

5. Why do we age? Eventually cells stop being replaced “Apoptosis”
Cell death
“We die because out cells die.”
William R. Clark

6. “C” Terms Chromosomes Chromatid Long threads of genetic material
Found in nucleus
Chromatid
One side of a duplicated chromosome

7. “C” Terms Centromere NOTE
Structures that hold sister chromatids together
NOTE
2 sister chromatids = 1 duplicated chromosome

8. “C” Terms Chromatin DNA tnagled around a histone (a protein)
Condensed chromatin = chromosome

9. Huh?
C. Duplicated chromosome
A. DNA
B Chromatin
histone

10. “C” Terms Centrioles Small protein bodies In cytoplasm
Animal cells only

11. Cell Division in a Nutshell
Before:
Chromosome duplicates = 2 sister chromatids
During:
Sister chromatids separate
After:
2 “daughter” cells
Genetically identical

12. Cell Cycle
Mitotic phase
10%
Interphase
90%

13. Interphase Made up of three phases: What happens? G1, S, G2
Things necessary to divide

14. Interphase G1 Phase S Phase G2 Phase More Cell Growth
8-10 hours
S Phase
DNA replication
Chromosome replication
6-8 hours
G2 Phase
More Cell Growth
Centriole replication
4-6 hours

15. Mitotic Phase Mitosis Cytokinesis Division of nucleus (chromosomes)
Occurs after interphase
Cytokinesis
Division of cytoplasm
Creates 2 daughter cells
Occurs at the end of mitosis

16. Mitosis Phases IPPMAT Interphase Prophase Prometaphase Metaphase
Anaphase
Telophase
IPPMAT

17. Task IPPMAT Draw a diagram of mitosis
Label 6 phases & give each a short description
IPPMAT

18. Interphase “Resting Phase” Precedes mitosis Prepares cell for division
Cell NOT dividing
Precedes mitosis
Prepares cell for division
How?

19. Early Prophase Centrioles: Chromosomes now visible Make spindle fibres
Move towards opposite plates
Chromosomes now visible

20. Late Prophase Centrioles reach poles
Nuclear membrane (envelope) & nucleolus start to disappear

21. Metaphase Spindle fibres attach to centromeres
Duplicate chromosomes line up at equator
Guided by spindle fibers

22. Anaphase Spindle fibers retract Pull sister chromatids apart
Towards opposite polls

23. Telophase Chromatin reappears Nuclear membrane & nucleolus reappear
Cytokinesis occurs
Result
Two daughter cells

24. What phases do you see? B A C D

25. Cytokinesis Why would it occur differently in animal and plant cells?
Plant cells have a rigid cell wall!

26. Cytokinesis Animal Cells Cell membrane pinches inward
Creates cleavagefurrow
Think:
Pull a string around a balloon
Plant Cells
Cell Plate forms between two new nuclei
Becomes cell wall

27. Cytokinesis

28. Cytokinesis

29. Plant vs. Animal – Another Difference?
Centrioles not present in plant cells
What makes spindle fibers in plant cells?
Form from cytoskeleton

32. Concept Map