1. Mitosis
Unit 5

2. What is Mitosis? Mitosis is the division of the nucleus
This is how we get new cells from existing cells

3. Limits to Cell Growth
There are two reasons cells divide rather than continue to grow:
The larger the cell becomes, the more demands the cell places on its DNA
Larger cells have more trouble moving enough nutrients and wastes across the cell’s membrane

4. 1. DNA “Overload”
Cell Demands
DNA
Nucleus
This is like a normal cell

5. + 1. DNA “Overload” Cell Demands DNA Nucleus
This is like a stressed out cell that needs to divide

6. Exchanging Materials TOWN LIMIT (Cell membrane)
This is like a normal cell

7. Exchanging Materials TOWN LIMIT (Cell membrane)
This is like a stressed out cell that needs to divide

8. This is like each new town getting it’s own “genetic library”!
Division of the Cell
Cells divide before they get too large.
The process by which cells divide into two “daughter” cells is called cell division.
This is like each new town getting it’s own “genetic library”!

9. The Cell Cycle
During the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells, each of which begins the cycle again.
There are 4 phases:
G1 phase
S phase
G2 phase
M phase

10. Cell increases in size, synthesizes new proteins and organelles

11. Chromosomes are replicated and DNA synthesis takes place

12. Usually the shortest phase
Usually the shortest phase. Many of the organelles and molecules required for cell division are produced

13. Mitosis is further divided into 4 phases and cell division occurs at the end

14. 4 Phases of Mitosis
Prophase
Metaphase
Anaphase
Telophase

15. Prophase Longest part of Mitosis (50-60% of the time)
Chromosomes become visible
Centrioles near the nuclear envelope move toward opposite poles
Condensed chromosomes become attached to spindle fibers at their centromeres
Nucleolus disappears and the nuclear envelope breaks down

16. Metaphase
Chromosomes line up across the center of the cell (metaphase plate)
Microtubules connect the centromeres of each chromosome to the two poles of the spindle

17. Anaphase Centromeres split
Sister chromatids separate toward spindles on opposite sides of the cell

18. Telophase
Once distinct chromosomes begin to disperse into a tangle of dense material
Nuclear envelope re-forms around each cluster (2) of material
Spindle breaks apart
Nucleolus visible in each daughter nucleus
Mitosis is complete

19. End of Mitosis. What’s Next?
What we’ve got:
2 nuclei with duplicate chromosomes in the cytoplasm of a single cell
Final task:
Divide the cytoplasm

20. What is division of the cytoplasm called?
The division of the cytoplasm is called cytokinesis

21. Cytokinesis
In animal cells the cell membrane draws inward and is pinched off forming two separate cells
In plants, a cell plate forms between the nuclei, turns into a separating membrane and eventually a cell wall