Interphase

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Interphase

• Replication of chromsomes
• Replication of centrosomes

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Prophase I

• Chromosomes Coil
• Spindle Forms
• Homologous Chromosomes pair together and Form a
  Tetrad.
• A Tetrad is composed of two sister chrmoatids.
• Crossing Over can happen here.

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The end of Prophase I
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Metaphase I

• The Spindle Fibers pull the tetrads into the
  middle.
• Note that homologous chromosomes are lined up
  side by side as tetrads unlike mitosis where the
  sister chromatids are lined up on the equator
  independent of each other.

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Anaphase I

• Homologous chromosomes, each with its two
  chromatids, separate and move to opposite ends of
  the cell.
• Centromeres hold the sister chromatids together
  and unlike mitosis, they do not split.
• This ensures that each new cell will received
  only one chromosome from each pair.

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The End of Anaphase I
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The beginning of telophase
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Telophase I

• Spindle is broken down.
• Chromosomes uncoil.
• Cytoplasm divides to yield two new cells.
• Each new cell has only half of the genetic
  information from the original cell because it has
  only one chromosome from each homologous pair.
• However, another division is needed because each
  chromosome is doubled consisting of two sister
  chromoatids.

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Mid-Telophase I
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Cytokinesis
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The Result of Meiosis I
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Meiosis II

• The newly formed cells in some organisms undergo
  an short interphase yet not DNA replication takes
  place
• The events of Meiosis II are identical to the
  events of mitosis.

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Meiosis II Prophase II
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Telophase II
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Telophase II
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Meiosis has produced four haploid cells each
different from each other.
Cytokinesis
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