Biology Lecture: Mitosis vs. Meiosis

Introduction

• Vocabulary terms often sound similar: chromosome, chromatid, chromatin, transcription, translation, mitosis, meiosis.
• Importance of understanding similarities and differences between mitosis and meiosis.
• Video provides a side-by-side comparison to aid understanding.

Overview

• Both mitosis and meiosis involve the creation of new cells.
• Mitosis:
  • Results in body cells.
  • Ends with two identical, diploid cells.
• Meiosis:
  • Results in gametes (sperm and egg cells).
  • Ends with four non-identical, haploid cells.

Starting Cell

• Starting cell for both processes is diploid (2n):
  • Human cells: 46 chromosomes (23 from each parent).
• Interphase:
  • Chromosomes are duplicated.
  • Duplicated chromosomes still counted as one due to centromere attachment.
  • Important for duplicating chromosomes before mitosis/meiosis.

Illustration

• Diagrams often simplified to 6 chromosomes for visualization.
• Example: mosquitoes have 6 chromosomes.

Stages of Mitosis and Meiosis

• Acronym PMAT for stages: Prophase, Metaphase, Anaphase, Telophase.
• Meiosis: stages occur twice with a number indicating the cycle (e.g., Prophase I, Prophase II).

Mitosis

• Prophase: Chromosomes condense and become visible.
• 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.
• Cytokinesis: Cytoplasm splits, creating two diploid cells.

Meiosis

Meiosis I

• Prophase I: Chromosomes match with homologous pairs, crossing over occurs.
• Metaphase I: Chromosomes line up in pairs.
• Anaphase I: Whole chromosomes pulled to opposite sides.
• Telophase I: Chromosomes at opposite ends, new nuclei form.

Meiosis II

• Prophase II: Chromosomes condense, no homologous pairing or crossing over.
• Metaphase II: Chromosomes line up single file.
• Anaphase II: Chromatids pulled to opposite sides.
• Telophase II: Chromosomes at opposite ends, new nuclei form.
• Cytokinesis: Ends with four non-identical haploid cells.

Result of Meiosis

• Gametes are haploid: 23 chromosomes in humans.
• Sperm and egg cells combine to form a diploid zygote, starting mitosis.

Conclusion

• Understanding mitosis and meiosis is crucial for comprehending cell division and organism growth.
• Amoeba Sisters Reminder: Stay curious!