Biology Lecture: Mitosis vs. Meiosis

Overview

• Vocabulary terms: Chromosome, Chromatid, Chromatin, Transcription, Translation, Mitosis, Meiosis.
• Focus: Side-by-side comparison of Mitosis and Meiosis.
• Objective: Understanding the differences and similarities between Mitosis and Meiosis.

Cell Division Basics

• Mitosis

  • Produces body cells.
  • Results in two identical diploid cells.

• Meiosis

  • Produces gametes (sperm and egg cells).
  • Results in four non-identical haploid cells.

Starting Cell

• Both processes start with a diploid cell (2n).
• Human diploid cells contain 46 chromosomes (23 pairs).

Interphase

• Occurs before both Mitosis and Meiosis.
• Chromosomes duplicate during this phase.
• 92 chromatids after duplication but still considered 46 chromosomes.

Stages of Mitosis and Meiosis (PMAT)

• Prophase

  • Mitosis: Chromosomes condense.
  • Meiosis I: Chromosomes form homologous pairs and crossing over occurs.

• Metaphase

  • Mitosis: Chromosomes line up in single file in the cell center.
  • Meiosis I: Homologous pairs line up in the center.

• Anaphase

  • Mitosis: Chromatids are pulled apart to opposite ends of the cell.
  • Meiosis I: Homologous chromosomes are pulled apart.

• Telophase

  • Mitosis & Meiosis I: New nuclei form around chromosomes at each cell end.

Cytokinesis

• Follows Telophase, splitting the cytoplasm.
• Mitosis: Results in two diploid cells.
• Meiosis II: Results in four haploid gametes.

Meiosis II

• Prophase II: Chromosomes condense without homologous pairing.
• Metaphase II: Chromosomes line up in single file line.
• Anaphase II: Chromatids are pulled apart.
• Telophase II: New nuclei form around chromatids.
• Followed by Cytokinesis, resulting in four non-identical haploid cells.

Conclusion

• Gametes (sperm and egg) are haploid (23 chromosomes in humans).
• Fertilization combines sperm and egg to form a diploid zygote (46 chromosomes), which grows via mitosis.
• Encouragement to stay curious about biological processes.