Lecture Notes: Mitosis by Professor Dave

Overview of Mitosis

• Mitosis is the process of cell division occurring throughout the body.
• It's essential for producing two identical cells from one parent cell.
• Mitosis is a part of the cell cycle, specifically involving genome copying and cell growth for division.

Phases of Mitosis

1. Prophase

   • Chromatin becomes tightly coiled, forming chromosomes.
   • Chromosomes consist of sister chromatids linked by a centromere.
   • Mitotic spindle begins forming from two centrosomes and microtubules.
   • Centrosomes have radial arrays of microtubules called asters.
   • Microtubules push centrosomes apart as cytoskeleton disassembles.

2. Prometaphase

   • The nucleus breaks apart.
   • Microtubules cover the area where the nucleus was.
   • Microtubules attach to kinetochores (proteins at centromeres).
   • A tug of war begins arranging chromosomes.

3. Metaphase

   • Centrosomes settle at cell poles with asters attaching to the plasma membrane.
   • Chromosomes align along the metaphase plate.
   • A checkpoint ensures all chromatids are attached correctly to the spindle.
   • Activation of regulatory protein complex allows progression past the M checkpoint.

4. Anaphase

   • Cohesins cleaved by enzyme separase.
   • Sister chromatids separate into individual chromosomes.
   • Chromosomes pulled by motor proteins to opposite cell ends.
   • Microtubules disassemble, elongating the cell.

5. Telophase

   • Formation of two new nuclei from original nucleus fragments.
   • Chromosomes loosen up slightly.
   • Completion of microtubule disassembly.
   • Result: Two genetically identical nuclei.

Cytokinesis

• Follows telophase to complete cell division.
• Cytoplasm divides, leading to two distinct cells.
• Cleavage furrow forms at the metaphase plate.
• Actin microfilaments create a drawstring effect to pinch the cell in two.

Importance of Mitosis

• Essential for cell production in skin renewal, wound healing, and childhood growth.
• Produces all somatic cells except the first fertilized egg cell.

Next Topic

• Transitioning to learn about gamete production, a different process from mitosis.