Cell Division: Mitosis and Meiosis

Mitosis

• Function:

  • Embryonic development
  • Tissue growth post-birth
  • Replacing damaged or dying cells

• Process Overview:

  • Involves one division
  • Results in two daughter cells
  • Daughter cells are diploid (23 pairs of chromosomes)
  • Each pair contains one maternal and one paternal chromosome

• Phases of Mitosis:

  1. Prophase
     • Chromatin condenses into chromosomes
     • Chromosomes consist of two identical sister chromatids
     • Nuclear envelope dissolves
     • Spindle fibers grow from centrioles
  2. Metaphase
     • Chromosomes align at cell's center
  3. Anaphase
     • Chromatids split and migrate to opposite cell ends
  4. Telophase
     • Nuclear envelopes reform
     • Cell division completes

Meiosis

• Function:

  • Produces gametes (eggs and sperm)

• Process Overview:

  • Involves two successive divisions
  • Results in four daughter cells
  • Daughter cells are haploid (23 unpaired chromosomes)

• Phases of Meiosis:

  • Meiosis I:
    1. Prophase I
       • Chromosomes condense
       • Crossing over: chromatids exchange DNA sections, creating new gene combinations
    2. Metaphase I
       • Homologous chromosomes align at cell center
       • Independent assortment occurs
    3. Anaphase I
       • Chromosome pairs separate
    4. Telophase I
       • Cell divides into two haploid daughter cells
  • Meiosis II:
    1. Prophase II
       • Cells prepare for another division
    2. Metaphase II
       • Chromosomes align at cell center
    3. Anaphase II
       • Chromosomes pulled apart into chromatids
    4. Telophase II
       • Cells divide
       • Results in four haploid daughter cells

• Outcome:

  • Male and female gametes with 23 unique single-stranded chromosomes
  • Genetic variability in humans

• Fertilization:

  • Gametes merge to form a zygote with 46 chromosomes
  • Zygote development occurs through mitosis