Why does a cell divide?

1. The Cell CycleSB2e E? What are the advantages and disadvantages of sexual and asexual reproduction? • Why does a cell divide? • New cells replace dead cells • Cells can’t be too big because: • materials can not be transported fast enough • Proteins can not be produced fast enough • Volume increases faster than surface area • O2, waste and nutrients can not diffuse fast enough • For growth • For development • For repair • For asexual reproduction • For gamete production • Sperm or eggs

2.   The Cell Cycle Section 10-2 M phase G1 phase S phase G2 phase Go to Section:

3. Interphase • Nucleus clearly seen • Period of growth and repair: G1 • DNA is in the form of chromatin • DNA is replicated: S phase • Centrioles duplicate • In plant cells asters duplicate

4. Interphase Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

5. Mitosis–The Division on Nuclear Material • Prophase • Metaphase • Anaphase • Telophase

6. Prophase-1st stage of Mitosis + Prometaphase • Chromatin coils to form visible chromosomes • Nuclear membrane and nucleolus begin to disappear • Spindle fibers form between centrioles • Prometaphase:Chromatids attach to spindle fibers at centromeres

7. Prophase Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

8. Metaphase • Chromosomes move to equator • Centrioles reach opposite poles

9. Metaphase Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

10. Anaphase • Centromeres split due to replication • Sister chromatids separate • Chromosomes move towards poles

11. Anaphase Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

12. Telophase • Chromosomes reach opposite poles • Nucleolus and nuclear membrane begin to reappear • Chromosomes begin to uncoil into chromatin • Cleavage-pinching in of cell membrane

13. Telophase Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

14. Cytokinesis Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

15. Division of Cytoplasm Cytokinesis • Animals • Cytoplasm pinches near equator • Two new cells form

16. Cell plateforming • Plants • Plasma membrane does not pinch • Cell plate forms across equator • Animals • Cytoplasm pinches near equator • Two new cells form

17. INTERPHASE PROPHASE Centrosomes(with centriole pairs) Early mitoticspindle Centrosome Fragmentsof nuclearenvelope Kinetochore Chromatin Centrosome Spindlemicrotubules Nucleolus Nuclearenvelope Plasmamembrane Chromosome,consisting of twosister chromatids

18. METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Cleavagefurrow Nucleolusforming Metaphaseplate Nuclearenvelopeforming Spindle Daughterchromosomes

19. Results • Guarantees genetic continuity • Two new cells with chromosomes identical to parent cell are formed

20. http://www.youtube.com/watch?v=lpAa4TWjHQ4 http://www.youtube.com/watch?v=gwcwSZIfKlM http://www.youtube.com/watch?v=I5uFuvkN97I Rap song: http://www.youtube.com/watch?v=pOsAbTi9tHw

21. 1. The stage when Chromosomes become visible________________ 2. The stage of growth & Repair,_________ 3. The stage when the chromosomes are moving to opposite ends.__________ 4. The stage where the centromeres split ________________ 5. DNA is copied_________________ 6. 2 new daughter nuclear membranes begin to appear__________________ 7. Each chromatid becomes a separate chromosome________________

22. True/False • 8. Cell size is important in the cell cycle? • 9. The nucleolus is present in Interphase, Prophase, Telephase, & Cytokenesis? • 10. Chromosomes become attached to spindle fibers during prophase? • 11. Write the order of the stages in the cell cycle.

23. Answers • 1. Prophase • 2. Interphase • 3. Anaphase • 4. anaphase • 5. Interphase • 6. Telephase • 7. anaphase • 8. T 9. T 10. T • 11. I/PMAT/C

24. Cancer • Uncontrolled growth of cells • Mutation in the gene that regulates growth and division • Lifestyles risks/Carcinogen • Tobacco • UV radiation • Alcohol • Diet • Chemotherapy and radiation

25. Petri dish showing normal division of cells. • 3rd dish shows cells separated in middle of dish. • 4th & 5th dish show how the cells will grow and divide to fill up the whole dish and stop. • If the 5th dish held cancer cells then they would not stop but continue to grow over the edges/rim of the petri dish.