The Cell Cycle and Mitosis - PowerPoint

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					      The Cell Cycle and Mitosis:

                    “You Complete Me”
          A process where one parent cell gives
             rise to two daughter cells- exact
                replicas of the original cell.



Genome British Columbia, 2004       www.genomicseducation.ca
                     The Cell Cycle
• Every cell goes through a process of
  growth, this is called the cell cycle.
• New cells start at G1 or Gap 1, go on
  to an S phase (where DNA is
  synthesized in preparation of
  Mitosis), and then G2 or Gap 2
  before Mitosis or Cell division.
• Some cells will no longer divide and
  they exit the cell cycle in G1(neurons,
  muscle cells, fat cells do this)
• As one cell enters Mitosis, two cells
  exit which are exact replicas or
  clones of the original “parent” cell.
Purpose: to replenish dead or dying
  cells, to allow an organism to grow
  and develop
                                          Interphase




• This phase encompasses all of the G1,S, and G2 phases of the cell
  cycle. The chromatin is diffuse.
• It may not look like much is going on here, but there is a lot of
  activity because the cell must prepare for Mitosis: protein synthesis,
  DNA synthesis, replication of other cellular structures too.

•   Onion root tip (on left side), whitefish (on right side)
Mitosis
    • Mitosis occurs in order for
      organisms to grow and
      develop. In order to
      replenish dead or dying
      cells such as skin cells,
      cells in the digestive tract
      and in the fertilized egg.
    • There are 4 main phases:
      Prophase, Metaphase,
      Anaphase, Telophase.
      Cytokinesis (division of
      the cytoplasm) follows
      and one cell becomes
      two.
Mitosis: Prophase
       • Major processes during
         this phase:
       • Chromosomes condense
         and form visible bodies
         (DNA was replicated in S
         phase)
       • Nuclear envelope breaks
         down

       •   Onion root tip (top photo), whitefish (bottom
           photo)
Mitosis: Metaphase
       • Chromosomes attached
         to spindle fibers line up in
         the middle (the equator)
         of the cell
       • Spindle fibers attach to
         the centromeres and
         other places along the
         chromosome

       •   Onion root tip (top photo), whitefish (bottom
           photo)
Mitosis: Anaphase
         • The last bit of DNA at the
           centromere replicates to
           allow the the centromere
           to split
         • The sister chromatids
           separate and are pulled
           to opposite sides of the
           cell

         •   Onion root tip (top photo), whitefish (bottom
             photo)
Mitosis: Telophase
      • Chromosomes now uncoil
      • Nuclear envelope reappears and
        surrounds the chromosomes
      Cytokinesis
      • The cytoplasm and all its contents are
        divided between the 2 daughter cells
        (cytoplasmic division)
      • The red arrow points at the newly
        developing plasma (cell) membrane that
        creates the 2 new daughter cells
      • The 2 daughter cells are exact replicas
        of the original parent cell – they are
        clones and have the exact same
        genetic make-up as the parent cell.

      •   Onion root tip (top photo), whitefish (bottom photo)
Answers:
A. Telophase   B. Prophase   C. Cytokinesis   D. Metaphase
                                 D                           C
                                 B
                                                             A
      Can you identify these stages?
                   Summary
• One parent cell begins the journey through the
  cell cycle and 2 new identical daughter cells
  emerge from one cycle.
• Mitosis occurs regularly in tissues that require
  new cells continuously such as skin cells, hair
  follicles, the lining of the digestive tract and in a
  newly fertilized egg.
• This process is important as it allows for an
  organism to grow and develop over its lifespan
  and replenishes dead or dying cells in certain
  tissues.
        Acknowledgements:
• Images taken from the following sites:
  – http://biog-101-
    104.bio.cornell.edu/BioG101_104/tutorials/cell
    _division.html
  – http://www.accessexcellence.org/AB/GG/mito
    sis2.html
  – http://www.biology.arizona.edu/cell_bio/tutoria
    ls/cell_cycle/cells3.html