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10T2K©
Cell Division 6 7 8 9 10

2. Thing 1: Three kinds of cell division
Bacteria divide by binary fission (prokaryotic fission).
The cell grows, the DNA duplicates, and the cell pinches in half.
Some eukaryotic somatic cells (body cells) divide by meiosis to make gametes (sperm and egg).
Gametes have half the chromosomes of the somatic cell that produced them.
Eukaryotic cells reproduce by mitosis and cytokinesis.

3. Binary Fission

4. Meiosis Four sex cells (gametes) with 1 copy of each chromosome
(haploid)
One body (somatic) cell with 2 copies of each chromosome
(diploid)

5. Thing 2: The eukaryotic cell cycle
Interphase: when a cell is active and may be preparing to divide.
Mitosis: division of the nucleus.
Cytokinesis: division of the cytoplasm to make two cells.

6. Thing 3: Purposes of mitosis
Mitosis makes daughter cells that are genetically identical to the original cell.
Mitosis is how single-celled eukaryotes reproduce.
Mitosis is how multicellular eukaryotes grow.
Mitosis is how multicellular eukaryotes replace worn-out cells.

7. Thing 4: The steps of interphase
Interphase starts with G1
The cell is not preparing to divide.
After G1 is S phase
Each chromosome duplicates to become two chromatids connected at the centromere.
After S is G2
Final preparations are made for mitosis

8. S Phase Gets You from A to B

9. Interphase Plant Cells

10. Thing 5: Mitosis begins with prophase
In prophase:
The nuclear membrane (nuclear envelope) and nucleolus go away.
The duplicated chromosomes become visible as they condense.
The spindle, made of microtubules (mostly), starts to form.

11. Prophase

12. Plant Cell in Prophase

13. Thing 6: Metaphase comes after prophase
In metaphase, spindle fibers push and pull duplicated chromosomes to the middle (equator) of the spindle.

14. The Mitotic Spindle

15. The Mitotic Spindle at Metaphase

16. Metaphase in a Plant Cell

17. Thing 7: Anaphase comes after metaphase
In anaphase, the two halves of the duplicated chromosomes separate from each other and move to opposite poles of the spindle.

18. Anaphase

19. Anaphase in a Plant Cell

20. Thing 8: Telophase comes after anaphase
In telophase, the events of prophase are reversed:
Nuclear envelopes and nucleoli form.
Chromosomes decondense.
The spindle disassembles.

21. Telophase

22. Telophase in a Plant Cell

23. Thing 9: Cytokinesis in animal cells
Cytokinesis is the division of one cell with two nuclei into two cells with one nucleus each.
In animal cells, a cleavage furrow pinches the cell into two cells.

24. Cytokinesis in an Animal Cell

25. Cytokinesis in an Animal Cell

26. Thing 10: Cytokinesis in plant cells
In plants, the cells do not pinch in half.
A cell plate forms between the two nuclei, building a cell wall between them.

27. Cytokinesis in a Plant Cell

28. Cytokinesis in a Plant Cell