1. The Cell Cycle What is the cell cycle?
What is mitosis – or cell division?
What happens in each stage?

2. Cell Cycle Cells grow and divide
Why do you think cells need to stay relatively small?

3. Why can’t cells just keep growing and growing?

4. Most cells are small because
Large cells place large demands on DNA – the DNA can’t “keep up”
Large cells have trouble exchanging nutrients and wastes through the cell membrane – material has to travel too far

5. On the other hand…
REALLY small cells like bacteria cells are not able to have specialized parts (organelles)
bacteria brain cell

6. The advantages of being larger (or multicellular)
Can SPECIALIZE!!!

7. When will a cell divide?
The surface area: volume ratio limits cell size. If a cell gets too big, it must divide to survive.
If a cell gets too big, it will undergo mitosis.

8. Cell Cycle Interphase Mitosis cell is growing and doing its thing
Cell division

9. Five Phases of the Cell Cycle
G1 – 1st growth phase
S – synthesis interphase
G2 – 2nd growth phase
M – mitosis
C – cytokinesis division

10. Interphase - G1 Stage 1st growth stage
Cell carries on normal activities

11. Two identical copies of DNA
Interphase – S Stage
Synthesis stage
DNA is copied
Two identical copies of DNA
Why does the cell need 2 copies? What would happen if it did not have 2 copies?
Original DNA

12. Interphase – S Stage
Why does the cell need 2 copies? What would happen if it did not have 2 copies when it got ready to divide?

13. Interphase – G2 Stage 2nd Growth Stage
Extra organelles & proteins are synthesized to prepare for division

14. Mitosis: Division of the Nucleus
Used for growth and repair
Occurs in somatic (body) cells
Produces two new cells identical to the parent

15. Mitosis – 4 stages Prophase Prepare to divide Metaphase Middle
Anaphase Apart
Telophase The End

16. Prophase DNA condenses to form visible chromosomes
Mitotic spindle forms
Nuclear membrane dissolves

17. Metaphase
Chromosomes line up at the equator (middle)

18. Anaphase
Sister chromatids are pulled apart by spindle fibers

19. Telophase Sister chromatids at opposite poles Spindle disassembles
Nuclear envelope reforms

20. Cytokinesis division of the cytoplasm
cell divides into two identical daughter cells

21. What phase?

22. What phase?

23. What phase?

24. What stages?