Chapter 10 Mitosis and Cytokinesis by xiaocuisanmin

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									Mitosis & Cytokinesis

Chapter 10
Mitosis




          Mitosis
    Cell Division

¡ In eukaryotes, cell division occurs in two
  major stages.
¡ The first stage, division of the cell nucleus, is
  called mitosis.
¡ The second stage, division of the cell
  cytoplasm, is called cytokinesis.
        Why do cells divide by
        Mitosis?
¡   Growth of the
    organism
¡   Repair of tissue
    damage
¡   Replacement of
    old cells
¡   Reproduction of
    some single celled
    organisms (Which     Amobea
    ones?)               Reproducing
Which single celled organisms
reproduce by mitosis?

¡   The protists or member of the
    kingdom Protista
¡   They are eukaryotic cells & have a
    nucleus. Mitosis = division of
    nucleus.
¡   Bacteria DO NOT divide by mitosis
    because they don’t have a nucleus.
¡   Bacteria reproduce via binary fission
Cells produced by Mitosis…….
        Skin
               ¡   Are called
                   daughter cells.
               ¡   Are identical to
                   the original cell
               ¡   Are identical to
                   each other
               ¡   Have the same #
                   of chromosomes
               ¡   Have an identical
                   chromosome
                   makeup
           A Duplicated Chromosome
                                  centromere


one chromatid


    its sister
   chromatid

                 One chromosome in the duplicated state
Diploid vs. Haploid Cells
¡   Diploid=
    l   A cell that has 2 sets of chromosomes
    l   One set came from each parent (mom
        and dad)
    l   Chromosomes come in pairs
    l   Humans have 23 pairs of
        chromosomes for a total of 46
        chromosomes per cell
    l   Somatic Cells are body cells (all
        except sperm and egg) and are
        diploid
Diploid vs. Haploid Cells

¡ Haploid   =
  l A cell with 1 set of chromosomes
  l Gametes or sperm or egg are
    haploid.
  l In humans, gametes contain 23
    chromosomes
Stages of Mitotic Cell Division

¡ Prophase  = “1st”
¡ Metaphase = “middle”

¡ Anaphase = “apart”

¡ Telophase = “far or
  separate”
          Interphase
¡   “Intermission”
¡   Normal metabolic
    (cell) activities
¡   Major state of the
    cell cycle.
¡   Cell spends 90% of
    time here
¡   DNA is in the form
    of chromatin, not
    coiled into
    chromosomes
¡   The nucleus appears
    solid. A nucleolus
    can sometimes be
    seen.
Late Interphase
           ¡ The cell prepares
             for mitosis
           ¡ DNA doubles
             (replicates) and
             forms sister
             chromatids
           ¡ Centrioles
             double in animal
             cells
Prophase   ¡ Nuclear
             membrane
             disappears
           ¡ Replicated
             DNA is
             condensed
           ¡ Chromosomes
             form and can
             be seen
           ¡   Spindle fibers
               start to form
Metaphase

            ¡   Chromosomes
                line up at that
                equator or
                middle of the
                cell
            ¡   The ends of
                the
                chromosomes
                point toward
                the ends or
                the poles of
                the cell.
Spindle & spindle fibers: Pull
apart the sister chromatids




                    Spindle
                    fibers
Anaphase
       ¡   Chromosomes
           move to opposite
           poles
       ¡   Centrioles are at
           the poles in
           animals
       ¡   Spindle apparatus
           is at the pole in a
           plant
Telophase
            ¡   Chromosomes
                gather at opposite
                ends of the cell and
                lose their distinct
                shape.
            ¡   Cell plate or new
                cells membranes
                form
            ¡   Nucleus
                reappears
Cytokinesis:
cytoplasm divides & splits apart
     Return to Interphase
¡ New daughter cells each
  resume the cell cycle in G1 of
  interphase.
¡ They will each have a period of
  growth and normal cell activity
    before they each divide.
    Cytokinesis




Mitosis is over, and     Band of microfilaments at the     The contractions
the spindle is now     former spindle equator contracts.   continue and cut
  disassembling.                                            the cell in two.
  Cytokinesis in Plants
             ¡   In plants, a structure known as the cell
                 plate forms midway between the divided
                 nuclei.                   Cell wall
Cell plate
Stages of Mitosis
    Plant versus Animal Mitosis
Plant:             Animal:
¡ Cell wall from   ¡ No cell wall
  cell plate in    ¡ Cell
  telophase          membrane
¡ Spindle            cytokinesis
  apparatus        ¡ Centrioles
 Cancerous cells……...
1.Divide too many
  times
2.Divide into more
  than two cells!
¡ Masses of cells =

¡ “tumors”

¡ benign

¡ malignant

								
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