Phases of Mitosis

Overview

• Mitosis is the division of the nucleus to create two identical daughter cells.
• Essential for growth, repair, and maintenance of cells.
• Part of the cell cycle, which includes:
  • Interphase: Cell growth and DNA duplication.
  • M phase: Includes mitosis and cytokinesis.

Cell Cycle Phases

• G1 Phase: Cell grows.
• S Phase (Synthesis): DNA is duplicated.
• G2 Phase: Further cell growth.
• G0 Phase: Resting phase; cells like nerve/muscle cells do not divide.

Interphase

• Not technically part of mitosis.
• DNA and centrosomes are duplicated.

Mitosis Phases

1. Prophase

   • DNA condenses into chromosomes.
   • Mitotic spindle begins to form.
   • Centrosomes move apart.

2. Prometaphase

   • Nuclear envelope fragments.
   • Microtubules attach to kinetochores on chromosomes.

3. Metaphase

   • Chromosomes line up at the metaphase plate in the cell’s center.
   • "Meet in the middle."

4. Anaphase

   • Sister chromatids separate and move to opposite poles.
   • "A" for Apart.
   • Ensures equal DNA distribution.

5. Telophase and Cytokinesis

   • Formation of new nuclei around chromosomes at each pole.
   • Cells elongate and the cleavage furrow or cell plate forms, dividing the cell.
   • Cytokinesis completes the division, resulting in two daughter cells.

Key Structures and Functions

• Cell Membrane: Divides into two during cytokinesis.
• Nuclear Envelope: Disintegrates in prometaphase, reforms in telophase.
• Centrosomes: Organize microtubules that form the mitotic spindle.
• Chromosomes: DNA condensed and organized for division.
  • Sister Chromatids: Identical copies connected by a centromere.
• Kinetochore: Protein complex at centromere where spindle fibers attach.

Summary

• Mitosis ensures equal division of DNA for cell replication.
• Acronym to remember phases: IPPMATC (Interphase, Prophase, Prometaphase, Metaphase, Anaphase, Telophase, Cytokinesis).
• Essential for growth and maintenance of organism's cells.

• Visualization: Onion cells are used in labs to observe mitosis due to distinguishable chromosomes.
• Mitosis as a "movie": Continuous and dynamic process rather than discrete steps.

These notes cover the key points mentioned during the lecture on mitosis, providing a comprehensive study guide.