The Cell Cycle

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The Cell Cycle
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I. Background

• The ability of organisms to reproduce their kind
  is one characteristic that best distinguishes
  living things from nonliving matter
• The continuity of life from one cell to another
  is based on the reproduction of cells via cell
  division
• The division process occurs as part of the cell
  cycle

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II. Cell Division Functions

• The division of a unicellular organism reproduces
  an entire organism, increasing the population
• Cell division on a larger scale can produce
  offspring for some multi-cellular organisms
• Cell division is also central to the development
  of a multi-cellular organism that begins as a
  fertilized egg or zygote
• Multi-cellular organisms also use cell division
  to repair and renew cells that die from normal
  wear and tear or accidents

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III. The Cell Cycle

• The Cell Cycle involves a period of cell division
  and a period of intermission
• Interphase is used in cells just before and
  shortly after cell division has occurred
• Interphase is used to
• Complete metabolic functions and add duplicate
  organelles
• Transcribe DNA so that proteins can be made
• Replicate DNA so that future divisions result in
  identical cells

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• Interphase is the longest phase of the cell cycle
  and varies in length by type of cell
• Interphase is followed by mitosis

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IV. Anatomy of a Chromosome
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V. Mitosis

• Mitosis follows Interphase and consists of 4
  distinct phases
• Prophase
• chromosomes condense and coil into thick, short
  strands which become visible
• Nuclear envelope dissolves
• Animals centrioles move to opposite ends of the
  cell (poles) and send out spindle fibers to
  attach to the centromere of each chromosome
• Plants lack centrioles and the spindles form
  directly from the microtubules in the cytoplasm

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• 2. Metaphase
• - chromosomes are led by the spindle fibers to
  the middle of the cell
• - chromosomes are arranged single file
• 3. Anaphase
• - spindle fibers pull the centromeres in
  opposite direction and split them
• - the separated chromosomes migrate to either
  pole

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• 4. Telephase
• - the nuclear envelope reappears
• - chromosomes begin to unravel
• - animal cell membrane begins to constrict
  until a cleavage furrow is formed and separation
  is complete
• - plant a cell plate forms as the Golgi sends
  out vesicles filled with polysaccharides the
  plant cells adds cellulose and finishes the cell
  wall