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Asexual Reproduction

Asexual Reproduction. Mitosis. Mitosis is the process in which the nucleus divides to form two new nuclei. How does mitosis differ in plants and animals?. 1. How do little elephants grow up to be BIG elephants?. Why do animals shed their skin?.

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Asexual Reproduction

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  1. Asexual Reproduction Mitosis Mitosis is the process in which the nucleus divides to form two new nuclei. How does mitosis differ in plants and animals? 1

  2. How do little elephants grow up to be BIG elephants?

  3. Why do animals shed their skin?

  4. The process of asexual reproduction begins after a sperm fertilizes an egg.

  5. Three reasons why cells reproduce by asexual reproduction: 1. Growth 2. Repair 3. Replacement

  6. Animated Mitosis Cycle http://www.cellsalive.com/mitosis.htm • Interphase • Prophase • Metaphase • Anaphase • Telophase & Cytokinesis

  7. Interphaseoccurs before mitosis begins • Chromosomes are copied (# doubles) • Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy(sister chromosome) change to sister chromatids at end of this phase CELL MEMBRANE Nucleus Cytoplasm

  8. 4 single-stranded chromosomes Forms of DNA Unwound DNA • Chromatin • Chromosomes • Chromatids DNA wound or coiled • Replicated DNA – held together by centromeres • 2 chromosomes – count centromeres • 4 chromatids

  9. Interphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

  10. Prophase 1st step in Mitosis • Mitosis begins (cell begins to divide) • Centrioles(or poles) appear and begin to move to opposite end of the cell. • Spindle fibers form between the poles. • Chromosomes are visible Centrioles Sister chromatids Spindle fibers

  11. Prophase Plant Cell Animal Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

  12. Metaphase 2nd step in Mitosis • Chromatids (or pairs of chromosomes) attach to the spindle fibers. • They line up in the “middle” or equator Centrioles Spindle fibers

  13. Metaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

  14. Anaphase 3rdstep in Mitosis • Chromatids (or pairs of chromosomes) separate and begin to move apart to opposite ends (“poles”) of the cell. Centrioles Spindle fibers

  15. Anaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

  16. Telophase4th step in Mitosis • Two new nuclei form. • Chromosomes appear as chromatin (threads rather than rods). • Mitosis ends. Nuclei Nuclei Chromatin

  17. Telophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

  18. Cytokinesisoccurs after mitosis • Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes. • Cells are identical to each other and to the original only smaller

  19. Animal Mitosis -- Review

  20. Plant Mitosis -- Review

  21. Cell Cycle

  22. - Cell Division The Cell Cycle 23

  23. MitosisAnimation http://www.cellsalive.com/mitosis.htm

  24. CANCERuncontrolled mitosis Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun. Cell that reproduce by asexual reproduction reproduce constantly.

  25. Why would cells just make copies? If DNA gets damaged, cells stop listening to correct instructions – make WRONG protein (enzymes) mutations – changes in DNA bases Mutagens (carcinogens) – cause mutations: • cigarette smoke • pollution • age • Genetics • heat • UV radiation • chemical exposure • benzene, toluene, asbestos • radiation exposure

  26. When is mitosis a BAD thing When cells reproduce & they are not needed these cells take over organs, but don’t do the right job they just keep making copies “starve” other cells/tissues cancer – uncontrolled mitosis damages organs

  27. Tumors Benign tumor abnormal cells remain at original site as a lump most do not cause serious problems &can be removed by surgery

  28. Tumors Malignant tumor cells leave original site - metastasizes carried by blood system to other tissues start more tumors damage functions of organs throughout body

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