Cell Division and Mitosis

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Cell
Division
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• Cell Division Date
• Summary

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Why divide a cell?

• To allow an organism to
• increase the surface area to volume ratio of the
  cell and decrease diffusion distances
• grow
• heal
• make reproductive cells

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The SA/V Ratio and Transport
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The Cell Cycle

• Interphase
• G1, S, G2
• Mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis

Cell Cycle Practice
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Interphase

• G1First Gap
• cell growth before DNA replication (biomolecules
  synthesized)
• S
• Synthesis
• DNA replication
• Proteins for DNA packaging are made
• G2
• Second Gap
• preparation for division, proteins driving
  mitosis made

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Chromosomes

• Chromo Colored
• Soma Body
• Each chromosome duplicates in preparation for
  mitosis
• Sister chromatids remain attached

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Chromosome Structure

• Chromatid
• Centromere
• Chromatid

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Mitosis and Meiosis

• Mitosis division of the nucleus to enable cells
  to maintain their number of chromosomes to make
  replicate cells (2n? 2n) Growth and Repair
• Meiosis division of the nucleus to allow cells
  to half their number of chromosomes to make
  reproductive cells (2n? n)

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Prophase
Interphase

• Preparing to divide
• Chromosomes become visible
• Nuclear envelope breaks up
• Spindle apparatus forms
• Centrioles move apart to opposite poles
• New tubulin subunits form the spindle

Interphase
Prophase
HeLa Cells
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Metaphase
Electron micrograph

• Lining up for division
• Chromosomes interact with microtubules on spindle
  apparatus
• Kinetochore Attachment at centromeres
• Microtubules pull on chromosomes and they line up
  at center of cell

Immunofluorescence
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Anaphase

• Moving Apart
• Separation of sister chromatids
• Microtubules shorten and pull chromatids to
  opposite poles

Immunofluorescence
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Telophase

• Separating cells
• Chromosomes arrive at spindle poles
• New nuclear membranes form
• Two nuclei form
• Cytokinesis/Cell Plate

Immunofluorescence
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Cytokinesis

• Cells moving
• Between late anaphase and end of telophase
• In plants cell plate forms
• Vesicles fuse
• In animals cleavage
• Cleavage furrow - depression forms at cells
  midsection

Cytokinesis image from Quantitation of the
distribution and flux of myosin-II during
cytokinesis Douglas N Robinson, Guy Cavet, Hans M
Warrick and James A Spudich
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Cell Plate

• Golgi apparatus and cytoskeleton
• Vesicles fuse to form Cell Wall

Phragmoplast cell plate from http//botit.botany.w
isc.edu/images/130/Mitosis/Allium_Root_Prep._Slide
s/phragmoplast_cell_plate.php?240,204
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Cleavage

• Interactions between cell membrane and
  cytoskeleton

Images of various embryos from Somatic budding
in Drosophila / cytokinesis in sea urchins George
von Dassow and Victoria Foe http//celldynamics.or
g/celldynamics/events/workshops/archive/2003/cytom
od_abstracts/GvD_VDF/