Mitosis Lecture Notes

Overview of Mitosis

• Mitosis is the process of cell division.
• Occurs throughout the body for growth and repair.
• Results in two identical cells with complete genetic information.
• Part of the cell cycle, following the G2 phase.

Phases of Mitosis

1. Prophase
   • Chromatin coils into chromosomes with sister chromatids linked by a centromere.
   • Mitotic spindle forms, consisting of centrosomes and microtubules.
   • Aster microtubules surround each centrosome.
   • Centrosomes are pushed apart.
2. Prometaphase
   • Nuclear envelope disintegrates.
   • Microtubules invade nuclear area.
   • Microtubules attach to kinetochores on centromeres.
   • Chromosomes start organizing.
3. Metaphase
   • Centrosomes at opposite poles.
   • Chromosomes align at the metaphase plate.
   • Checkpoint ensures proper attachment of sister chromatids to spindle.
   • Passage through M checkpoint allowed once aligned.
4. Anaphase
   • Separase enzyme cleaves cohesins, separating sister chromatids.
   • Chromatids move to opposite cell poles.
   • Cell elongates.
5. Telophase
   • Two new nuclei form.
   • Chromosomes decondense.
   • Microtubules disassemble.
   • Completion of mitosis with two identical nuclei.

Cytokinesis

• Final step following mitosis.
• Cytoplasm divides resulting in two distinct cells.
• Begins with a cleavage furrow formed by actin microfilaments.

Importance of Mitosis

• Essential for producing new skin, healing wounds, and growth.
• All somatic cells (except the first fertilized egg) are produced by mitosis.

A Look Ahead

• Mention of gametes and introduction to meiosis, a different process for producing reproductive cells.