1. Mitosis, Cytokinesis, Cell Cycle

2. I) Why Do Cells Divide? 1) Too Big a) Too Big to Transport Materials b) Too Big to Control 1.72 3.52 cm cm

3. Surface to Volume Math Surface Area of a Cube = Length x Width x 6 Volume of a Cube = Length x Width x Height 1 cm cube: Surface Area = 1 cm x 1 cm x 6 = 6 cm 2 6 Volume = 1 cm x 1 cm x 1 cm = 1 cm 3 1 2 cm cube: Surface Area = 2 cm x 2 cm x 6 = 24 cm 2 24 = 3 Volume = 2 cm x 2 cm x 2 cm = 8 cm 3 8 1

4. I) Why Do Cells Divide? 2) Too Small a) Surface Area to Volume Ratio Too Small b) Cell Membrane Too Small to Exchange Materials

5. II) When Do Cells Divide? 1) Growth – Somatic (body) cells undergo mitosis for growth. 2) Maintenance – Somatic cells use mitosis to repair damage. 3) Asexual Reproduction – Mitosis is the process used by some organisms to reproduce (budding, etc…)

7. III) Cell Cycle: I – M & C – I (x 2) 1) Interphase: G 1, S, G 2 2) G 1 = Growth of Cell (After Division) 3) S = Synthesis (of DNA) and Continued Growth 4) G 2 = Growth and Prepare to Divide 5) M = Mitosis (PMAT) 6) C = Cytokinesis = Division of Cytoplasm

8. IV) Chromatin vs Chromosomes 1) Both GENETICALLY Identical DNA 2) Same Nucleotide Sequence 3) Chromatin Uncoiled 4) Chromosome Coiled

9. V) Chromosomes 1) Centromere: a) Holds Sister Chromatids together b) Spindle Fibers Attach 2) Sister Chromatids: a) Half of a Chromosome b) Contain Alleles

10. 3) Chromosomes (Replication) a) S phase b) Chromosomes Replicated (Copied) before Mitosis

11. MITOSIS DIVI SION O F T H E NUC L EUS

12. VI) Mitosis: Prophase 1) Prophase: First True Stage of Mitosis a) DNA coils into Chromosomes b) Chromosomes are Connected by a Centromere making One Chromosome with Sister Chromatids c) Centrioles appear d) Centrioles move to opposite poles e) Nuclear Membrane breaks down, releasing Chromosomes (DNA) f) Spindle Fibers form (Microtubules) at Centrioles g) Spindle fibers attach the Centrioles (Anchor) to the Centromere of the Sister Chromatids (DNA)

13. VI) Mitosis: Metaphase 2) Metaphase: “Middle” Stage of Mitosis a) Spindle Fibers attached to the Centromeres of the Chromatids move the Chromosomes to the middle b) Sister Chromatids are aligned in the Middle of the Cell

14. VI) Mitosis: Anaphase Anaphase: Third Stage of Mitosis a) Spindle Fibers attached to the Centromeres of the Chromatids separate the Sister Chromatids b) Sister Chromatids are pulled to Opposite ends of the Cell c) Separated Chromatids are now called Individual Chromosomes

15. VI) Mitosis: Telophase 4) Telophase: Reverse of Prophase a) Spindle Fibers release the Centromeres of the New Chromosomes b) The Centrioles and Spindle fibers all “Disappear” c) TWO Nuclear Membranes Form surrounding the Chromosomes at EACH end of the Cell d) The Chromosomes Uncoil back into strands of Chromatin (DNA)

16. VII) Cytokinesis (NOT MITOSIS) Cytokinesis: Not Mitosis, Division of Cytoplasm a) Cytoplasm Divides b) New Cell Membrane is Formed c) Two New “Daughter” Cells are Formed with: 1) Equal Number of Chromosomes 2) Approximately Equal Cytoplasm and Organelles d) Back into Interphase at G 1

17. Summary of Mitosis Prophase: Chromosomes condense Nuclear envelope disappears centrosomes move to opposite sides of the cell Spindle forms and attaches to centromeres on the chromosomes Metaphase Chromosomes lined up on equator of spindle centrosomes at opposite ends of cell Anaphase Centromeres divide: each 2-chromatid chromosome becomes two 1-chromatid chromosomes Chromosomes pulled to opposite poles by the spindle Telophase Chromosomes de-condense Nuclear envelope reappears Cytokinesis: the cytoplasm is divided into 2 cells