Cell Division

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Cell Division

• Section 8.2

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• All cells are derived from the division of
  pre-existing cells
• Cell division is the process by which cells
  produce offspring cells

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Cell division in Prokaryotes

• Binary fission- the division of a prokaryotic
  cell into 2 offspring cells

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Cell division in Eukaryotes

• Mitosis- results in new cells with genetic
  material that is identical to that of the
  original cell
• Meiosis- reduces the chromosome number by half in
  new cells

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The cell cycle

• The repeating set of events that make up the life
  of a cell
• Interphase- the time between cell divisions
• M phase- mitosis
• Cytokinesis- the division of the cytoplasm of the
  cell

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Interphase

• G1 phase-offspring cells grow to mature size
• S phase- the cells DNA is copied
• G2 phase- the time gap following the S phase and
  preceding cell division
• G0 phase- cells do not copy their DNA and dont
  prepare for cell division

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Mitosis

• Divided into 4 phases prophase, metaphase,
  anaphase, and telophase

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Prophase

• First phase of mitosis
• Centrosomes- appear next to the disappearing
  nucleus
• Centrioles- found in animal cells

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• Spindle fibers- made of microtubles radiate from
  the centrosomes in preparation for mitosis
• Mitotic spindle- equally divides the chromatids
  between the 2 offspring cells

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• Kinetochore fibers- attach to kinetochore
• Kinetochore- disk-shaped protein
• Polar fibers- extend across the dividing cell
  from centrosome to centrosome

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Metaphase

• Second phase of mitosis
• The kinetochore fibers move the chromosomes to
  the center of the dividing cell

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Anaphase

• Third stage of mitosis
• Chromatids of each chromosome separate at the
  centomere

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Telophase

• Fourth stage of mitosis
• Spindle fibers disassemble
• Chromosomes return to a less tightly coiled
  chromatin state

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Cytokinesis

• Cleavage furrow- pinches the cell into 2 cells
  (animal cells)
• Cell plate- membrane-bound cell wall (plant cells)

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