1. M Phase – Cell Division Divided into two parts Mitosis Cytokinesis
division of the cell’s nucleus
Cytokinesis
division of the cell’s cytoplasm

2. M Phase – Cell Division Chromatin Chromosome Chromatids
all of the chromosomes in the nucleus
Chromosome
a single piece of DNA in the nucleus
Chromatids
two identical “sister” replicated chromosomes, held together by a centromere

3. Chromosomes
Individual Chromosomes
Chromatin

4. Chromosome Visibility
Chromosomes become visible during cell division as they condense (coil) to become more manageable during separation.

5. Please flip your notes to the opposite side of the page.

6. Chromosomes a One chromosome (unduplicated) centromere one chromatid
two sister
chromatids
one chromatid
b One chromosome (duplicated)

7. Flip your page again. Attempt to label each blank on your notes.
1. _____________________
5. _________________
2. _________________
3. _____________________
4. _____________________

8. Now correct each label on your notes.
1. chromosome
5. centromere
2. sister chromatids
4. chromatid
3. chromatid

9. Maintaining Chromosome Number
When cells divide, each cell duplicates an entire copy of its chromatin.
When the cell divides, each “daughter cell” receives one complete copy of the chromatin.
This allows each cell to have the same number of total chromosomes.

10. Maintaining Chromosome Number
chromosome (unduplicated) in cell
Maintaining Chromosome Number
same chromosome (duplicated) prior to mitosis
mitosis & cytokinesis
chromosome (unduplicated)
in daughter cell
at interphase

11. Maintaining Chromosome Number
The two new daughter cells will be genetic twins, and they will genetically be identical to the cell they came from.

12. Mitosis Mitosis occurs in 4 phases: Prophase Metaphase Anaphase
Telophase

13. Mitosis
Prophase

14. Mitosis Prophase Chromatin condenses into individual chromosomes
Nuclear envelope breaks down
Centrioles separate
Centrioles – specialized structures in animal cells that help pull apart duplicated chromosomes

15. Mitosis
Metaphase

16. Mitosis Metaphase Chromosomes line up across the center of the cell
Each chromosome is connected to a spindle fiber at its centromere
Spindle fibers –microtubules fibers that move chromosomes
in animals, centrioles pull on the spindle fibers
in plants, fibers attach directly to the cell wall

17. Mitosis
Anaphase

18. Mitosis
Anaphase
Sister chromatids separate into individual chromosomes and are moved apart
As the chromatids are no longer connected, the centromeres that connected them no longer exist.

19. Mitosis
Telophase

20. Mitosis
Telophase
Chromosomes gather at opposite ends of the cell and lose their distinct shapes
Two new nuclear envelopes form
Spindle dissolves
Cells begin to separate in preparation for cytokinesis

21. What is visible in mitosis that is unable to be seen in interphase?

22. Cytokinesis the cytoplasm of the cell is divided in half
the cell membrane grows to surround each new daughter cell

23. Mitosis & Cytokinesis 1. Interphase 2. Prophase 3. Metaphase
4. Early Anaphase
5. Late Anaphase
6. Telophase
7. Cytokinesis
8. Interphase

26. Mitosis & Cytokinesis
Animation

27. Cytokinesis in Plants the cell is divided in half by a cell plate
cell plate – a newly formed cell wall

28. Mitosis in Animals vs. Plant Cells
Differently shaped cells
Plants
Square-ish
Animals
Round-ish
Differences in cytokinesis
No cell wall/cell plate in animal cells

29. Summary
Why is mitosis important? In other words, why is it important that a cell can copy its DNA (during Synthesis) and divide its DNA (during Cell Division)?