CELL DIVISION

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CELL DIVISION
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Cell Theory
All cells arise from existing cells
Cells are the basic unit of life
CELLS
All organisms are made up of one or more cells
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Cell Cycle (Division Cycle)

• Series of events that take place to replicate the
  cell
• ____________ and ____________
• Mitosis body cells (somatic)
• Meiosis sex cells (reproductive cells)

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Mitosis

• From the Greek, mitos
• Chromosome Structure
• http//www.johnkyrk.com/chromosomestructure.html

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Mitosis One cell becomes two

• Why Mitosis?

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Mitosis
IDENTICAL

• Nucleus---- Nucleus1 Nucleus 2
• Cytoplasm ------Cytoplasm 1 Cytoplasm2

w/ chromosomes
chromosomes
chromosomes
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Examples of Somatic cells

• Hair
• skin
• Bones
• Blood
• connective tissue (cartilage)

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Cell cycle

• Interphase
• Chromosomes are duplicated
• Mitosis
• Identical chromosomes are separated
• And pulled to opposite sides of the cell
• Cytokinesis
• Division of the cell

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Cell cycle

• Stage Interphase
• Step one G1
• Cell grows, accumulates nutrients, reproducing
  mitochondria, cytoskeleton disassembles.
• Step two S DNA Synthesis
• http//www.dnaftb.org/dnaftb/20/concept/index.html
  
• http//www.johnkyrk.com/index.html
• Step three G2 DNA Synthesis is complete

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Mitosis

• Prophase (coil to shape)
• Chromatin starts to organize, condenses and
  twists to into chromosomes.
• the nucleolus and nuclear membrane fade
• Mitotic spindle begins to form outside nucleus.
• Cytoskeleton begins to disassemble
• http//micro.magnet.fsu.edu/cells/mitosisjava/mito
  sisjava.html

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http//micro.magnet.fsu.edu/cells/mitosisjava/mito
sisjava.html
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Mitosis

• Metaphase (align and attach)
• Tension applied by the spindle fibers
• aligns all chromosomes at middle of cell.
• Microtubules attach to spindles, and to the
  centromeres of each chromosome.

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Mitosis

• Anaphase (divide and drag)
• Centromere divides, one for each chromosome.
• Chromatids are dragged by microtubules (spindle
  fibers) to opposite poles of the cell.
• Cell becomes stretched and elongated

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MITOSIS

• Telophase ( contract and expand)
• Chromosomes arrive at the poles.
• The spindle fibers that have pulled them apart
  disappear.
• Nuclear envelopes form around chromosomes.

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Mitosis

• Cytokinesis (separate and go)
• Cytoplasm divides
• Spindle fibers begin breaking down
• Microtubules reorganize into a new cytoskeleton
  for the return to interphase.

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Homework

• Draw a chromosome and label its parts.
• Draw the first stage of somatic cell division
  Interphase.

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What happens when something goes awry?