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The Cell Cycle

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Chapter 12 The Cell Cycle Roles of cell division reproduction growth/maintenance repair Eukaryotic chromosome Cell Cycle Cell Cycle Interphase period when the ... – PowerPoint PPT presentation

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Title: The Cell Cycle


1
Chapter 12
  • The Cell Cycle

2
Roles of cell division
  • reproduction
  • growth/maintenance
  • repair

3
Eukaryotic chromosome
4
Cell Cycle
5
Cell Cycle
  • Interphase period when the cell is not dividing
  • consists of
  • G1 gap (growth period)
  • S synthesis of DNA
  • G2 gap (growth, preparation for division)

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7
Mitosis (M)
  • Prophase centrioles migrate to opposite poles,
    nucleolus breaks down, spindle begins to form,
    chromatid pairs get shorter, compact, more
    visible
  • Prometaphase - nuclear membrane breaks down,
    spindle fibers extend to centromeres
  • Metaphase spindle fibers have attached to
    kinetochore of ea. sister chromatid at the
    centromere sister chromatids are aligned at
    metaphase plate (equator)

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10
Mitosis (M)
  • Anaphase ea. chromatid of sister chromatid pair
    is separated and pulled toward opposite poles
  • Telophase nuclear membrane nucleolus
    reappear, spindle breaks down, chromosomes get
    longer, thinner
  • cytokinesis division of cytoplasm

11
Differences in plant and animal cell cytokinesis
  • In animal cells, a contractile ring forms a
    cleavage furrow as the membrane pinches in to
    divide the 2 daughter cells
  • In plant cells, a cell plate forms as vesicles of
    the Golgi pinch off containing cell wall
    material, migrate to the metaphase plate,
    elongate, fuse to form a new cell wall to
    separate the 2 daughter cells

12
Cleavage furrow in an animal cell
13
Cell plate in a plant cell
14
Differences in prokaryotic eukaryotic cell
division
  • Prokaryotes (bacteria) divide by binary
    fission
  • circular DNA in a single chromosome
  • 1) DNA replicates
  • 2) Each copy is attached to cell membrane
  • at opposite ends of the cell
  • 3) Cell membrane forms between the 2
  • daughter cells being produced as
    growth
  • continues
  • 4) membrane pinches inward, new cell wall
  • material is deposited between 2
    daughter cells

15
Binary fission
16
Differences in prokaryotic eukaryotic cell
division
  • Eukaryotes (everything else) divide most
    commonly by mitosis

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18
Regulation of the cell cycle
  • controlled by regulatory proteins
  • checkpoints critical points where go/no go
    signals regulate processes
  • G1 checkpoint restriction point
  • -if it passes this point, it is
    destined to
  • continue through division
  • -if it doesnt pass this checkpoint, it
    goes into G0

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20
Regulation of the cell cycle
  • kinase enzyme that catalyzes transfer of PO4
  • from ATP to a target protein to
    activate or
  • inactivate it
  • Cdks cyclin-dependent kinases (active only
    when attached to a particular cyclin)
  • ex MPF (maturation promoting factor)
  • cyclins concentrations change cyclically

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22
Control systems
  • 1) density dependent inhibition (contact
    inhibition)
  • cells stop dividing when they come into
  • contact with one another (usu. due to
    growth
  • factor decrease)
  • 2) anchorage dependence require attachment
  • to substrate (like ECM of a tissue)

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Escaping normal controls
  • cancer cells unregulated growth of cells
  • -divide indefinitely as long as nutrients
    are
  • available immortal
  • results in tumor (mass)
  • -benign remains at original site
  • -malignant ability to spread
    (cancer)
  • unusual of chromosomes
  • aberrant metabolism
  • lost attachments (abnormal surface changes)

25
Escaping normal controls
  • metastasis spread beyond original site

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