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CELL DIVISION

CELL DIVISION. How do little elephants grow up to be BIG elephants?. Why do animals shed their skin?. Mitosis. Mitosis is the process in which the nucleus divides to form two new nuclei . How does mitosis differ in plants and animals?. 4.

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CELL DIVISION

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  1. CELL DIVISION

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

  3. Why do animals shed their skin?

  4. Mitosis Mitosis is the process in which the nucleus divides to form two new nuclei. How does mitosis differ in plants and animals? 4

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

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

  9. 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. Centrioles Sister chromatids Spindle fibers

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

  11. Metaphase 2nd step in Mitosis • Chromatids (or pairs of chromosomes) attach to the spindle fibers. Centrioles Spindle fibers

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

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

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

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

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

  17. Cytokinesisoccurs after mitosis • Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.

  18. Animal Mitosis -- Review

  19. Plant Mitosis -- Review

  20. Body Cells • Most of the life of a eukayortic cell is spent in a period of growth or development (interphase). • Nerve and muscle cells are always in interphase.

  21. Cell Cycle

  22. - Cell Division The Cell Cycle 23

  23. Karyotypes • Display of chromosomes lined up in homologous pairs • Half inherited from male Half from female • Used for viewing #, size, shape, and banding • patterns of chromosomes

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

  25. Sexual vs. Asexual • Sexual reproduction: • 2 parents and one or many offspring with genetic diversity • Ex: sperm+egg=zygote, seed plants • Asexual reproduction: • 1 parent and one or many offspring which are an exact copy of the parent • Ex: vegetable that sprout, runners, hydra, sponges

  26. ASEXUAL REPRODUCTION

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

  28. Fertilization: when haploid sperm and egg meet, combining N chromosomes with N chromosomes = 2N zygote • Zygote: fertilized egg, 2N 23 23 46

  29. MEIOSIS

  30. Two types of cells • Body cells, non sex cells, they are diploid • “Diploid” or 2N: having two sets of chromosomes • “Haploid” or N: having one set of chromosomes (sex cells)

  31. Diploid vs. Haploid Exercises • Drosophilia have a diploid number of 8. What is the haploid? • Onions have a haploid number of 8. What is the 2N? • A horse’s 2N is 64. What is the 1N? • A body cell of an alligator has 32 chromosomes. Is this the diploid or haploid number? 4 16 32 Diploid

  32. II. Meiosis • Definition: cell division to produce egg (ovule) or sperm (pollen)

  33. Homologous Chromosomes: matching pair of chromosomes, one inherited from each parent

  34. General Process of Meiosis • MEIOSIS I (PMAT I &C) - Prophase I: homologous chromosomes meet up and form tetrads. Crossing over occurs. - Metaphase I: homologous chromosomes line up along the equator; the assortment among homologs is random

  35. INDEPENDENT ASSORTMENT

  36. CELL THEN GOES THROUGH “INTERKINESIS”- NO MORE DOUBLING OF CHROMOSOMES!!

  37. General Process of Meiosis • MEIOSIS II (PMAT II & C) - Starts with 2 haploid cells - Prophase, Metaphase, Anaphase, Telophase II and Cytokinesis serve to separate the sister chromatids - Ending Cells: 4 cells, each with haploid chromosomes

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