Meiosis and Mitosis

• Meiosis


  The type of cell division that produces four daughter cells contain half the amount of genetic material and are known as our sex cells or 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 from opposite poles
• Anaphase 1


  • Spindle fibers separate the homologous chromosomes in each tetrad and pull them to opposite poles
• Telophase 1


  • One chromosome from each homologous pair at separate poles, each chromosome still consists of sister chromatids
• Meiosis 2


  • DNA does not replicate before it begins
  • Sister chromatids separate and move to opposite poles
• Meiosis begins with a diploid cell
• Meiosis only produces gametes
• Gametes are genetically different haploid cells
• Crossing over results in genetic differences in gametes
• All gametes produced by meiosis are haploid
• During Anaphase 1 of Meiosis, how does the spindle fibers separate the chromosomes in each tetrad?

  by pulling them towards the opposite poles
• M phase


  The fourth and final phase of the cell cycle, where cell division occurs through mitosis and cytokinesis
• Mitosis


  Division of the nucleus
• Cytokinesis


  Division of the cytoplasm
• Phases of the cell cycle


  • G1
  • S
  • G2
  • M
• Mitosis

  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Prophase


  • Chromatin condenses into chromosomes
  • Spindle fibers form
  • Nucleolus and nuclear membrane disappear
• Metaphase


  • Spindle fibers align chromosomes along the cell equator that results in a sister chromatid being present on either side of the equator.
• Anaphase


  • Spindle fibers separate sister chromatids into two groups of chromosomes, pulling them toward the poles
• Telophase


  • Nucleolus and nuclear membrane reform
  • Chromosomes disperse into chromatin
• Cytokinesis in animal cells

  Inward movement of the cell membrane progressively pinches the cytoplasm until two daughter cells form
• Cytokinesis in plant cells


  Cell wall material assembles along the equator forming a cell plate that grows until it joins the existing cell membrane, separating the two halves into daughter cells
• The M phase always results in two identical daughter cells