Meiosis

• Meiosis

  The type of cell division that produces gametes
• Gametes


  Sex cells such as sperm cells in males and egg cells in females
• Meiosis

  1. Meiosis 1

  2. Meiosis 2
• Meiosis 1

  1. Prophase 1

  2. Metaphase 1

  3. Anaphase 1

  4. Telophase 1
• Meiosis 2

  1. Prophase 2

  2. Metaphase 2

  3. Anaphase 2

  4. Telophase 2
• Prophase 1

  • Diploid cell
  • Chromatin contains two uncoiled spread out sets of chromosomes
  • DNA replicates
  • Chromosomes condense into X-shaped
  • Homologous chromosomes pair up and bind forming a tetrad
  • Crossing over happens, exchanging segments of alleles
• Metaphase 1


  • Homologous chromosomes line up at the equator and attach to spindle fibers
• Anaphase 1


  • Homologous chromosomes separate and move to opposite poles
• Telophase 1


  • One chromosome from each homologous pair at separate poles
  • Sister chromatids no longer identical due to crossing over
  • Nuclear membrane reforms
  • Cytokinesis occurs
• Meiosis 1 outcome

  • Two genetically different haploid daughter cells
• Prophase 2


  • Nuclear membrane disappears
  • Spindle fibers fan out from centrioles
• Metaphase 2


  • Chromosomes line up at the equator and attach to spindle fibers
• Anaphase 2


  • Sister chromatids separate and move to opposite poles
• Telophase 2


  • Spindle fibers disappear
  • Nuclear membranes reform
  • Cytokinesis occurs
• Meiosis 2 outcome

  • Four genetically different haploid daughter cells
• Meiosis begins with a diploid cell
• Meiosis only produces gametes
• Gametes are genetically different haploid cells
• Crossing over during prophase 1 results in genetic differences in gametes
• All gametes produced by meiosis are haploid