Cell Division

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Cell Division
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Why do Cells divide?

• Overload its DNA
• Exchange of materials

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The Cell Cycle

• A series of events that a cell goes through as
  they grow and divide
• Cell grows
• Prepared to divide
• This time in between divisions is called
  Interphase
• Divides forming two daughter cells
• Each daughter cell repeats the cell cycle

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Chromosomes

• DNA is carried from one generation of cells to
  the next generation by chromosomes
• Chromosomes are made up of DNA and proteins

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Before Cell Division

• Each chromosome is replicated (copied), this
  results in two identical sister Chromatids.

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Mitosistug-of-war

• 4 phases
• Prophase,
• metaphase,
• anaphase,
• telophase

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Prophase

• Longest phase
• Chromosomes become Visible
• The centrioles, separate and take positions on
  opposite sides of the nucleus
• Centrioles acts as the anchors in the tug-of-war
• Spindles begin to form, and attach to the
  chromosomes
• Spindles are the ropes for the tug-of-war
• Nuclear envelope (membrane) breaks down

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Metaphase

• Shortest phase
• Chromosomes line up across the center of the cell
• tug-of-war is set and ready

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Anaphase

• The tug-of-war begins
• The centromeres begin to separate
• the Chromatids split, and become single
  chromosomes
• The chromosomes continue to move until they are
  at opposite sides of the cell

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Telophase

• The chromosomes begin to disperse and disappear
• The nuclear envelope (membrane) reforms around
  each cluster of chromosomes
• Spindles break apart and disappear
• Tug-of-war is over its a tie

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Mitosis is over, but cell division is not

• There is now one cell with two nuclei
  (nucleuses), each with a duplicate set of
  chromosomes
• Cell must go through Cytokinesis

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Cytokinesis

• The division of the cytoplasm
• Usually occurs at the same time as telophase
• In animal cells the cytoplasm pinches off
• In plant cells a cell plate forms which
  eventually becomes a membrane.

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The End Result

• Started with one cell
• Ended with two cells, exactly the same as each
  other and exactly the same as the original cell.

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Starts with 1 cell
2n

• End up with 2 identical cells

2n
2n