1. The Cell Cycle & Cell Division

2. The Cell Cycle

3. Cell Cycle and Cell Division
You started out as a single cell. This cell went through the cell cycle and cell division. Through this process, you developed into the person you are today.

4. Why do cells divide? Cells are not dividing all of the time.
Cells divide for 3 main reasons:
Growth
Repair
Reproduction in single-celled organisms

5. What are the phases of the cell cycle?
The Cell Cycle consists of Interphase and the Mitotic (M) Phase.
Interphase consists of the:
Gap 1 (G1) Phase
Synthesis (S) Phase
Gap 2 (G2) Phase

6. What happens during interphase?
Gap 1 (G1) Phase – Period of cell growth before the DNA is duplicated. New organelles are also made during this phase.
Synthesis (S) Phase – Period where the DNA is duplicated, therefore the chromosomes are duplicated (even though DNA has not yet condensed to form chromosomes)
Gap 2 (G­­2) Phase – Period after the DNA has duplicated. The cell now prepares for cell division.

7. Cell Cycle

8. MITOSIS

9. Mitosis
The process of cell division which results in the production of two daughter cells from a single parent cell.
The daughter cells are identical to one another and to the original parent cell.

10. Mitosis can be divided into stages
Interphase
Prophase
Metaphase
Anaphase
Telophase & Cytokinesis

11. Interphase The cell prepares to divide
Animal Cell
DNA replicated
Organelles replicated
Cell increases in size
Plant Cell
DNA replicated
Organelles replicated
Cell increases in size

12. Interphase Plant Cell Animal Cell
Photographs from:

13. Prophase The cell prepares for nuclear division
Animal Cell
Packages DNA into chromosomes
Plant cell
Packages DNA into chromosomes

14. Prophase Plant Cell Animal Cell
Photographs from:

15. Metaphase The cell prepares chromosomes for division
Animal Cell
Chromosomes line up at the center of the cell
Spindle fibers attach from daughter cells to chromosomes at the centromere
Plant Cell
Chromosomes line up at the center of the cell
Spindle fibers attach from daughter cells to chromosomes at the centromere

16. Metaphase Plant Cell Animal Cell
Photographs from:

17. Anaphase The chromosomes divide
Animal Cell
Spindle fibers pull chromosomes apart
½ of each chromosome (called chromotid) moves to each daughter cell
Plant Cell
Spindle fibers pull chromosomes apart
½ of each chromosome (called chromotid) moves to each daughter cell

18. Anaphase Plant Cell Animal Cell
Photographs from:

19. Telophase The cytoplasm divides
Plant Cell
DNA spreads out
2 nuclei re-forms
New cell wall forms between to nuclei to form the 2 new daughter cells (called a cell plate)
Animal Cell
DNA spreads out
2 nuclei re-forms
Cell membrane pinches in to form the 2 new daughter cells (called a cleavage furrow)

20. Telophase Plant Cell Animal Cell
Photographs from:

21. Mitosis Animation

22. Animal Mitosis -- Review
Interphase                                                             
Prophase                                                             
Metaphase                                                             
Anaphase                                                             
Telophase                                                             

23. Plant Mitosis -- Review
Interphase                                                             
Prophase                                                             
Metaphase                                                             
Anaphase                                                             
Telophase                                                             

24. MEIOSIS

25. One parent cell produces four daughter cells.
Meiosis
Meiosis is the type of cell division by which germ cells (eggs and sperm) are produced.
One parent cell produces four daughter cells.
Daughter cells have half the number of chromosomes found in the original parent cell

26. During meiosis, DNA replicates once, but the nucleus divides twice.

27. Four stages can be described for each division of the nucleus.
Meiosis
Four stages can be described for each division of the nucleus.

28. First division of meiosis
Meiosis I
First division of meiosis

29. First Division of Meiosis
Prophase 1: Each chromosome duplicates and remains closely associated. These are called sister chromatids.
Metaphase 1: Chromosomes align at the center of the cell.
Anaphase 1: Chromosome pairs separate with sister chromatids remaining together.
Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the chromosome pair.

30. Prophase I

31. Prophase I

32. Metaphase I

33. Telophase I

34. Second Division of Meiosis

35. Second Division of Meiosis
Prophase 2: DNA does not replicate.
Metaphase 2: Chromosomes line up at the center of the cell
Anaphase 2: Centromeres divide and sister chromatids move separately to each pole.
Telophase 2: Cell division is complete.
Four haploid daughter cells are formed.

36. Prophase II

37. Metaphase II

38. Telophase II

39. Meiosis

40. Meiosis Animation

41. Differences in Mitosis & Meiosis
Occurs in autosomal (non-sex) cells
Cell divides once
Two daughter cells
Diploid cells (full set of genetic information)
Meiosis
Occurs in sex cells
Cell divides twice
Four haploid (half set) daughter cells

42. Comparison Animations