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Understanding Mitosis and Meiosis Differences

Nov 15, 2024

Biology Lecture: Mitosis vs. Meiosis

Introduction

  • Vocabulary in biology can be confusing: chromosome, chromatid, chromatin, transcription, translation, mitosis, meiosis.
  • Focus: side-by-side comparison of mitosis and meiosis.
  • Both processes create new cells and involve cytokinesis (splitting of the cytoplasm).
  • Mitosis results in body cells; meiosis results in gametes (sperm and egg cells).

Starting Cell

  • Both mitosis and meiosis start with a diploid cell (2n).
  • Diploid: 2 sets of chromosomes (one from mom, one from dad).
  • Humans: 46 chromosomes (23 pairs).
  • Interphase: Cell duplicates chromosomes (92 chromatids), not part of mitosis/meiosis but essential for duplication.

Stages Overview: PMAT

  • PMAT: Prophase, Metaphase, Anaphase, Telophase.
  • Meiosis goes through PMAT twice (I and II).

Mitosis

  • Prophase:
    • Chromosomes condense (become visible/thickened).
  • Metaphase:
    • Chromosomes line up in the middle (single file).
  • Anaphase:
    • Chromatids are pulled away to opposite sides.
  • Telophase:
    • Chromosomes at opposite ends; new nuclei form.
    • Followed by cytokinesis to fully divide the cell.
  • Result: Two identical diploid cells (46 chromosomes each).
  • Purpose: Growth and repair.

Meiosis I

  • Prophase I:
    • Chromosomes condense and pair with homologous chromosomes (crossing over occurs, exchanging genetic info).
  • Metaphase I:
    • Chromosome pairs align in the middle.
  • Anaphase I:
    • Chromosome pairs pulled apart to opposite sides.
  • Telophase I:
    • Chromosomes at opposite ends; new nuclei form.
    • Followed by cytokinesis.

Meiosis II

  • Prophase II:
    • Chromosomes condense; no homologous pairing or crossing over.
  • Metaphase II:
    • Chromosomes align in the middle (single file).
  • Anaphase II:
    • Chromatids are pulled away.
  • Telophase II:
    • Chromosomes at opposite ends; new nuclei form.
    • Followed by cytokinesis.
  • Result: Four non-identical haploid cells (23 chromosomes each).
  • Purpose: Formation of gametes (sperm/egg).

Key Insights

  • Meiosis produces genetic diversity through crossing over and independent assortment.
  • Fertilization combines haploid sperm and egg to form a diploid zygote, starting mitotic divisions.

Summary: Understand the differences and similarities between mitosis and meiosis, the role of each in the life cycle, and the genetic implications of meiosis. Stay curious!

Full transcript