Lecture Notes: Mitosis by Professor Dave

Introduction

• Cell Cycle: Cells replicate their genome and prepare for division.
• Mitosis: Complex process of cell division occurring throughout the body.

Phases of Mitosis

1. Prophase

   • Chromatin coils into visible chromosomes.
   • Sister chromatids are linked by a centromere.
   • Mitotic spindle forms from centrosomes and microtubules.
   • Centrosomes have a radial microtubule array called an aster.

2. Prometaphase

   • Nuclear envelope disintegrates.
   • Microtubules attach to kinetochores on chromosomes.
   • Chromosomes start organizing for alignment.

3. Metaphase

   • Centrosomes position at cell poles.
   • Chromosomes align at the metaphase plate.
   • Checkpoint ensures chromatids attach to opposite spindle ends.
   • Activation of regulatory protein complex for M checkpoint passage.

4. Anaphase

   • Separase enzyme cleaves cohesins, separating sister chromatids.
   • Chromosomes pulled apart to opposite cell ends by motor proteins.
   • Cell elongates.

5. Telophase

   • Formation of two new nuclei.
   • Chromosomes begin to uncoil.
   • Mitosis completes with two identical nuclei.

Cytokinesis

• Cytoplasm division into two distinct cells.
• Cleavage furrow forms at metaphase plate.
• Actin microfilaments constrict to divide cell.

Biological Significance

• Cell Production: Mitosis creates new skin, heals wounds, supports growth in childhood.
• Somatic Cells: All except the first cell (formed by fertilization) are produced by mitosis.
• Reproductive Cells: Produced by a different process (meiosis).

Next Topic

• Understanding gamete formation through meiosis.