1. 300 MILLION CELLS DIE IN THE HUMAN BODY EVERY MINUTE
TODAY’S SCIENCE SMILE
300 MILLION CELLS DIE IN THE HUMAN BODY EVERY MINUTE

2. Mitosis

3. Mitosis
Mitosis takes place when a parent cell divides into 2 identical daughter cells.
Before mitosis takes place, DNA must be duplicated so that the daughter cell receives an exact copy from the parent cell.
Passing on genetic information through cell division is called genetic continuity.
Mitosis takes place in somatic (body) cells.

4. WHY DO CELLS DIVIDE?
WHO REMEMBERS???!!

5. THE THREE REASONS WE LOOKED AT…
GROWTH
REPAIR
REPRODUCTION

6. Overview on why they divide?
Cells must divide in order to function properly.
If cells become too large, the following problems arise:
The cell cannot take in enough nutrients to satisfy the cell’s requirements.
The nucleus cannot control the activities of a cell that is too large

7. The Cell Cycle
The cells spend most of their time growing, in a phase called Interphase.
When a cell needs to divide, it will enter the Mitotic phase.
The Cell Cycle is divided into 4 stages:
G1 Phase – Cell growth
S Phase – DNA is replicated
G2 Phase – Cell prepares for mitosis
M Phase (Cell division ) – cell undergoes mitosis

8. The Cell Cycle

9. Interphase
Interphase:
Chromosomes are not readily visible but appear as an irregular network of strands called chromatin
Nucleus is visible
Nuclear membrane is visible
Nucleoli are visible

10. Interphase

13. Mitosis THERE ARE FOUR STAGES IN MITOSIS
This is where cell division takes place!!!
Page in your textbook!!

14. First Stage - Prophase Prophase:
Centrioles move to opposite poles of the cell
Chromatin condenses into short, thick chromosomes
The replicated chromosomes become clearly visible and are held together at a single point called a centromere
Each identical strand is called a chromatid
The nuclear membrane breaks down
The nucleoli disappear
Spindle fibres begin to form around the centrioles
The spindle fibres attach to the centrioles
The chromosomes begin to move into the middle of the cell

15. Prophase

16. Second Stage - Metaphase
Chromosomes line up at the equator of the cell in a specific way
This area is sometimes called the metaphase plate

17. Metaphase

18. Third Stage - Anaphase Anaphase:
Chromosomes begin to separate into chromatids
The chromatids are held at the centromere by the spindle fibres
Each chromatid is pulled towards opposite poles of the cell
Anaphase ends when a complete set of chromatids arrives at each of the poles

19. Anaphase

20. Fourth Stage - Telophase
The daughter cells return to interphase conditions
The nuclear membrane reforms
Nucleoli reappear
Chromosomes elongate by uncoiling and become chromatin once again
The spindle fibres and centrioles disappear
Two nuclei are visible within a single cell

21. Telophase

22. End of Telophase - Cytokinesis
In animal cells, the cell membrane pinches inwards at the equator, producing a furrow
The furrow deepens until two separate cells are produced, each with their own nucleus and cytoplasm
The parent cell’s organelles are distributed to each of the daughter cells
In plant cells, a cell plate forms across the equator of the cell (begins in late anaphase)
Cellulose is added and eventually, a new cell wall divides the parent cell into two daughter cells (see text pg 164)

23. Now there are two cells!!!

24. Easy ways to memorize this:
Use a mnemonic:
Interesting People Make A Terrific Conversation
I Played Myself A Tune Clearly
Use a visual: “PMAT” P P

25. Or your hands!!!

26. Now watch the Animations

27. Using your handout, see if you can identify the stages of mitosis…….
NAME THE STAGES…
Using your handout, see if you can identify the stages of mitosis…….

28. FILL IN THE BLANKS
Use the words at the bottom of the handout too complete the story of mitosis.

29. I will be walking around to help!
Mitosis Matching
Step 1
Using the mitosis handout. Cut out the images at the bottom of the sheet.
Step 2
Match each image with the correct name in the circle above.
I will be walking around to help!

30. Homework Text: Read pgs ___________________
Complete questions _____________________
Or handout review sheet