Biology: Meiosis

• Sexual reproduction


  Organisms pass their genes to their offspring through this process
• Sexual reproduction

  1. Two gametes unite to form an embryo

  2. Embryo grows into an adult

  3. Adult passes genetic information to offspring
• Gametes


  Cells formed through meiosis
• Germline cells


  Cells that undergo meiosis to produce gametes
• Germline cells


  • Have two copies of each chromosome in diploid organisms
  • Undergo meiosis to produce haploid gametes with one copy of each chromosome
• Meiosis


  1. Interphase (G1, S, G2)

  2. Meiosis I (Prophase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis)

  3. Meiosis II (Prophase II, Metaphase II, Anaphase II, Telophase II, Cytokinesis)
• Meiosis I


  • Homologous chromosomes separate
  • Sister chromatids remain attached at centromere
• Meiosis II


  • Sister chromatids separate
  • No synapsis or crossing over of homologous chromosomes
• Prophase I


  • Chromosomes condense
  • Homologous chromosomes undergo synapsis and crossing over
  • Nuclear membrane breaks down
  • Centrosomes migrate to opposite poles
  • Microtubules attach to chromosomes
• Metaphase I


  • Synapsed chromosomes align at equator randomly
• Anaphase I


  • Homologous chromosomes separate and migrate to poles
• Telophase I and Cytokinesis


  • Cell divides into two daughter cells
• Prophase II


  • Chromosomes condense
  • Nuclear envelope breaks down
  • Spindle apparatus forms
• Metaphase II


  • Chromosomes align at equator randomly
• Anaphase II


  • Sister chromatids separate and migrate to poles
• Telophase II and Cytokinesis

  • Nuclear envelope reforms
  • Cytoplasm divides into four haploid daughter cells (gametes)
• Gametes from mother and father

  Fuse to produce diploid embryo
• Embryo development


  Grows through many cycles of mitosis