1. Cell Division

2. We all start out as a single cell.

4. Cytoplasm and organelles
That single cell has:
Cell membrane
Cytoplasm and organelles

5. Nucleus and a nuclear membrane
That single cell has:
Nucleus and a nuclear membrane

6. Chromatin (chromosomes)
That single cell has:
Chromatin (chromosomes)

7. Centrioles (only in animal cells)
That single cell has:
Centrioles (only in animal cells)

8. How do we become our multi-cellular selves?

9. That first single cell must divide!

10. One becomes two.

12. Two cells become four.

14. Four becomes eight. Eight becomes 16. 16 becomes 32.

15. And so on.

16. The process of cell division is called mitosis.

17. It happens in 6 phases.

18. Phase 1
Interphase

19. Interphase: onion root

20. Interphase: animal cell

21. Interphase: plant cell

22. Cell is performing its usual life functions, and is not dividing

23. Chromosomes are thin and thread-like (called chromatin at this stage)

24. Near the end of phase one, the chromosomes are duplicated

25. The chromosome count doubles

26. The original and copy chromosomes are attached at an area called the centromere

27. Phase 2
Prophase

28. Prophase: onion root

29. Prophase: animal cell

30. Prophase: plant cell

31. The chromosomes shorten and become rod-like. This makes them stronger.

32. The centrioles move to opposite ends of the cell

33. A mesh-like bridge forms between the two centrioles

35. In plants, the bridge forms without centrioles

36. The nuclear membrane breaks down

37. Phase 3
Metaphase

38. Metaphase: onion root

39. Metaphase: animal cell

40. Metaphase: plant cell

41. The centromeres attach the chromosomes to the mesh-like bridge

42. Phase 4
Anaphase

43. Anaphase: onion root

44. Anaphase: animal cell

45. Anaphase: plant cell

46. The centromere splits, allowing the chromosomes to separate from their copies

47. The chromosomes and the copies move away from each other on the mesh-like bridge, toward the centrioles

49. Phase 5
Telophase

50. Telophase: onion root

51. Telophase: animal cell

52. Telophase: plant cell

53. The chromosomes uncoil and become thread-like chromatin again

54. A nuclear membrane forms around the chromatin at each end of the cell

55. Phase 6
Cytokinesis

56. Cytokinesis:

57. The cell membrane pinches off equal amounts of cytoplasm

58. Each part contains a new nucleus, and there are two new cells!

59. The end of Cell Division!