Lecture Notes: Mitosis vs. Meiosis

Introduction

• Vocabulary confusion: Terms like chromosome, chromatid, chromatin, transcription, translation, mitosis, and meiosis can be confusing due to their similarity.
• Purpose of video: Side by side comparison of mitosis and meiosis (split screen format).
• Pre-requisite knowledge: Basic understanding of mitosis and meiosis.

Overview of Cell Division

• Mitosis: Results in body cells.
• Meiosis: Results in gametes (sperm and egg cells).
• Cytokinesis: Follows both processes to split the cytoplasm.

Starting Cell Conditions

• Diploid cells (2n): 2 sets of chromosomes, 46 total in humans (23 from each parent).
• Interphase: DNA duplication phase (not part of mitosis or meiosis), results in 92 chromatids.

Simplified Illustrations

• Use of 6 chromosomes: Easier visualization, e.g., mosquitoes have 6 chromosomes.

Stages of Mitosis and Meiosis

• Acronym PMAT: Prophase, Metaphase, Anaphase, Telophase
  • Mitosis: Goes through PMAT once.
  • Meiosis: Goes through PMAT twice (PMAT I and PMAT II).

Mitosis Stages

• Prophase: Chromosomes condense and become visible.
• Metaphase: Chromosomes line up in the middle (single file).
• Anaphase: Chromatids pulled apart to opposite sides.
• Telophase: Chromosomes at opposite ends; new nuclei form.
  • Cytokinesis: Splits cytoplasm, resulting in two identical diploid cells (46 chromosomes in humans).

Meiosis Stages

Meiosis I

• Prophase I: Homologous chromosomes pair up; crossing over occurs (recombinant chromosomes).
• Metaphase I: Chromosomes line up in pairs (not single file).
• Anaphase I: Chromosomes (not chromatids) pulled to opposite sides.
• Telophase I: Chromosomes at opposite ends; new nuclei form.
  • Cytokinesis: Splits cytoplasm.

Meiosis II

• Prophase II: Chromosomes condense (no homologous pairing or crossing over).
• Metaphase II: Chromosomes line up in single file.
• Anaphase II: Chromatids pulled apart.
• Telophase II: Chromosomes at opposite ends; new nuclei form.
  • Cytokinesis: Results in four non-identical haploid gametes (23 chromosomes each in humans).

Conclusion

• Gametes: Male gametes are sperm, female gametes are eggs.
• Zygote formation: Sperm + egg = diploid cell (zygote) that divides via mitosis to form a new organism.
• Encouragement: Stay curious!