Meiosis

Flashcards for the phases of Meiosis 1 and 2 

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Meiosis

  • Sexual reproduction
  • Causes genetic variation
  • The gametes of each parent fuse to form a zygote
  • When the gametes fuse, the chromosomes combine in one nucleus. This means that the chromosome number is diploid
  • The role of meiosis is to reduce the chromosome number by half, therefore making it haploid.
  • These phases are preceeded by Interphase 1, where DNA and organelles replicate. 
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Prophase 1

  • Chromatin undergo supercoiling
  • Homologous pairs of chromosome form bivalents
  • Non-sister chromatids wrap around each other - chiasmata 
  • Non-sister chromatids swap DNA - crossing over
  • Nucleolus disappears
  • Nuclear envelope disintegrates
  • Spindle forms
  • Can last for several days
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Metaphase 1



  • Bivalents join up across the equator
  • They are joined to spindle at centromeres
  • The chromosomes are ready to independently segregate
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Anaphase 1



  • Homologous chromosomes are pulled by the spindle to opposite poles
  • The centromeres don't divide
  • Chiasmata separate - the swapped lengths of DNA stay with their new chromosome 
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Telophase 1

  • Two new nuclear envelopes form
  • Brief interphase
  • In plants, the cell goes straight from anaphase 1 into meiosis 2
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Prophase 2

  • Nuclear envelope breaks down again
  • Nucleolus disappears
  • Chromosomes supercoil
  • Spindle form
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Metaphase 2

  • Chromosomes arrange themselves on the spindle, 90 degrees to how they were arranges in metaphase 1
  • Chromatids are randomly assorted
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Anaphase 2

  • Centromeres divide 
  • Chromatids are pulled to opposite poles
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Telophase 2

  • Nuclear envelopes reform around haploid daughter nuclei
  • In animals, 4 haploid cells form
  • In plants, a tetrad of four haploid cells is formed 
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