Lecture on Mitosis

Introduction to Mitosis

• Cell Cycle: Cells copy genome and grow in preparation for division.
• Mitosis: Complex process of cell division.
  • Results in two identical cells with complete genetic information.

Phases of Mitosis

1. Prophase

   • Chromatin becomes tightly coiled, forming visible chromosomes.
   • Sister chromatids linked by a centromere.
   • Formation of the mitotic spindle from centrosomes and microtubules.
   • Centrosomes with aster microtubules start to separate.

2. Prometaphase

   • Nuclear envelope breaks down.
   • Microtubules extend to kinetochores on chromosomes.
   • Organization geared towards aligning chromosomes.

3. Metaphase

   • Centrosomes at cell poles with asters.
   • Chromosomes aligned along the metaphase plate.
   • Checkpoint ensures correct attachment of chromatids to spindle.

4. Anaphase

   • Shortest phase.
   • Enzyme separase cleaves cohesins; sister chromatids separate.
   • Chromosomes pulled to opposite poles by motor proteins.
   • Cell elongates.

5. Telophase

   • Formation of two new nuclei from original nuclear fragments.
   • Chromosomes loosen, microtubules disassemble.
   • Completion of mitosis with two identical nuclei.

Cytokinesis

• Cytoplasm division completes cell separation.
• Initiated by a cleavage furrow by actin microfilaments.
• Ensures two distinct cells.

Significance of Mitosis

• Function: Produces new cells for skin, wound healing, and growth.
• Origin of Somatic Cells: All body cells (except the first, a fertilized egg) are produced by mitosis.

Transition to Gamete Production

• Mention of a different process for producing gametes (egg and sperm cells).