Chapter 5: Cell Division and Specialization

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Chapter 5 Cell Division and Specialization

• Section 5-2
• Cell Division

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Lets Review!

• What are the phases of the cell cycle?
• What happens in each phase?

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Mitosis

• The phases of the cell cycle that occur between
  cell divisions are known as interphase
• Interphase is made up of the G1, S, and G2 phases
  of the cell cycle
• Once the cell has reached its maximum size, it is
  triggered to enter the M phase - mitosis

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Mitosis

• Mitosis, or division of the nucleus, is divided
  into four phases
• Prophase
• Metaphase
• Anaphase
• Telophase
• After mitosis, cytokinesis divides the cytoplasm

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Prophase

• Longest phase of mitosis
• DNA coils into chromosomes (normally chromatin)
• The two identical copies of each chromosome
  created in the S phase are called chromatids
• Chromatids join at the centromere

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A Chromosome
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Prophase

• The nucleolus and the nuclear membrane disappear
• Centrioles (tiny structures found only in animal
  cells) move to opposite ends of the cell these
  will help to organize microtubules
• Spindle fibers form between them

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Prophase
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Metaphase

• Shortest phase of mitosis
• Chromosomes line up along the equator of the cell
• Centromeres of each chromatid pair attach to
  spindle fibers

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Metaphase
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Anaphase

• Chromatids separate at the centromere and move to
  opposite ends of the cell
• No longer called chromatids now called
  chromosomes again

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Anaphase
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Telophase

• Spindle fibers disassemble
• Chromosomes uncoil to chromatin
• New nuclear envelope forms around each set of
  DNA, creating two distinct nuclei

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Telophase
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Cytokinesis

• Cytoplasmic division
• Cell membrane pinches midway between 2 new nuclei
• This is called a cleavage furrow
• In plant cells, a cell plate also forms as an
  extension of the cell wall

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Cytokinesis
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Mitosis

• At the end of mitosis, one cell has split into
  two genetically identical daughter cells.

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Mitosis
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Animation!

• http//glencoe.mcgraw-hill.com/sites/0078695104/st
  udent_view0/unit2/chapter9/concepts_in_motion.html