1. Cell Cycle
Cell Division

2. Strawberry Division!

3. Why do cells need to divide?
Growth – so organisms can increase in size (natural selection theory)
Development – for cells to become specialized (e.g. create organs)
Repair – for cells to replace removed or dead cells (e.g skin cells)

4. Which cells divide the most? - Somatic Cells
Skin cells are dividing all day, everyday.
We lose around 30,000 to 40,000 skin cells a minute!
That’s 50 million skin cells lost in one day!

5. Cell Cycle – 3 Parts Interphase – cell growth takes place
Inter = enter
Mitosis – division of DNA(chromosomes)
mito = strong, powerful
sis = process
Cytokinesis – division of cytoplasm
cyto = cell
kinesis = movement

6. What is the 1st part of the cell cycle?
Interphase
G1 (growth stage one) : cell is growing & developing and making proteins
S (synthesis): DNA replication process
G2 (growth stage two): cell is making final preparations for cell division

7. Cell Cycle

9. What is the 2nd part of the cell cycle?
Mitosis
Prophase
Metaphase
Anaphase
Telophase

10. Mitosis
Prophase
-chromatin begins to coil into think, visible chromosomes

11. Mitosis
Metaphase
-spindles fibers line up chromosomes in the “middle”

12. Mitosis
Anaphase
-spindle fibers move chromosomes “apart”

13. Mitosis
Telophase
-chromosomes reach opposite ends
-centromere

14. Cytokinesis
Animal Cell
Plant Cell

15. Cytokinesis: Which cell is pictured?

16. What happens if the cycle is disrupted?
Gain-of-function mutations (oncogenes)
Loss of function
mutations (“tumor suppressor” genes)
proteins involved in regulating cell division events no longer appropriately drive progression from one cell cycle stage to the next
Example:
Cancer is uncontrolled cell division or inappropriate cell proliferation

17. Independent Activity
In ten minutes, you will be able to write 6 sentences using the following words:
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis