Mitosis vs. Meiosis: A Side-by-Side Comparison

Introduction

• Similar vocabulary terms in biology:
  • Chromosome
  • Chromatid
  • Chromatin
  • Transcription
  • Translation
  • Mitosis
  • Meiosis
• Importance of understanding differences and similarities between mitosis and meiosis.
• This video provides a split screen comparison of both processes.

Overview of Mitosis and Meiosis

• Both processes involve cytokinesis to divide the cytoplasm.
• Mitosis: results in body cells.
• Meiosis: results in gametes (sperm and egg cells).
• Starting cell is diploid (2n):
  • Humans: 46 chromosomes (23 from mom, 23 from dad).
• Interphase: important phase for duplicating chromosomes.
  • 46 chromosomes are duplicated, resulting in 92 chromatids (still counted as 46 chromosomes until they separate at centromeres).
  • Diagrams will use 6 chromosomes for simplicity.

Stages of Mitosis and Meiosis

• Stages summarized with the acronym PMAT:
  • Both processes go through these stages, but meiosis goes through them twice (labelled PMAT I and PMAT II).

Prophase

• Mitosis:
  • Chromosomes condense and become visible.
• Meiosis I:
  • Homologous chromosomes pair up.
  • Crossing over occurs, resulting in recombinant chromosomes.

Metaphase

• Mitosis:
  • Chromosomes line up in a single file line in the middle of the cell.
• Meiosis I:
  • Chromosomes line up in pairs in the middle of the cell.

Anaphase

• Mitosis:
  • Chromatids are pulled away to opposite sides.
• Meiosis I:
  • Homologous chromosomes are pulled apart, not chromatids.

Telophase

• Mitosis:
  • Chromosomes reach opposite ends, new nuclei form, and cytokinesis follows to split the cell into two identical diploid cells (46 chromosomes each).
• Meiosis I:
  • Similar to mitosis but results in two cells still containing pairs of chromosomes.

Meiosis II

• Prophase II:
  • Chromosomes condense in both cells, less eventful than prophase I.
• Metaphase II:
  • Chromosomes line up in a single file line.
• Anaphase II:
  • Chromatids are pulled away to opposite sides.
• Telophase II:
  • New nuclei form at opposite ends, followed by cytokinesis, resulting in four non-identical haploid cells (gametes).

Conclusion

• In males, meiosis produces sperm cells; in females, it produces egg cells.
• Resulting gametes have half the number of chromosomes (23 for humans).
• Fertilization of sperm and egg results in a diploid zygote, which undergoes mitosis to develop into an organism.
• Reminder to stay curious!