Phases of Mitosis

Introduction

• Mitosis is a biological process remembered by many.
• Purpose: Division of the nucleus to create two identical daughter cells from a parent cell.
• Part of the cell cycle which duplicates the cell.
• Mitosis ensures growth from a zygote to billions of cells and replaces dying cells.

Cell Cycle Overview

• Most time spent in Interphase (orange phase).
• Interphase Phases:
  • G1 Phase: Cell growth.
  • S Phase: DNA duplication.
  • G2 Phase: Further cell growth.
  • G0 Phase: Cells like nerve and muscle cells that don’t divide.
• M Phase: Mitosis, division of the nuclei.
• Outcome: Two cells that enter their own cell cycle.

Interphase Details

• Cells grow, duplicate DNA, and prepare for division.

Mitosis as a Movie

• Mitosis can be viewed like a movie with continuous events.
• Example: Sea urchin cell division.

Structures Involved

1. Cell Membrane

• Divides through a cleavage furrow.
• Results in two cells.

2. Nuclear Envelope

• Initially intact; fragments and re-forms during mitosis.

3. Centrosomes

• Composed of microtubules forming a spindle.
• Centrosomes replicate, move apart, and facilitate chromosome division.

4. Chromosomes

• DNA is tightly packed around histone proteins into chromosomes.
• Consists of sister chromatids connected at a centromere.
• Kinetochore proteins attach chromosomes to microtubules.

Mitosis Phases

Interphase

• DNA and centrosomes are duplicated.

1. Prophase

• Chromosomes condense.
• Mitotic spindle starts to form.

2. Prometaphase

• Nuclear envelope fragments.
• Microtubules attach to kinetochores.

3. Metaphase

• Chromosomes line up at the metaphase plate.

4. Anaphase

• Sister chromatids move apart to opposite poles.

5. Telophase and Cytokinesis

• New nuclei form.
• Cell elongates and divides via cleavage furrow (or cell plate in plants).

Conclusion

• Mitosis ensures equal DNA division, cell replication, and body's cell formation.
• Mnemonic for phases: IPPMATC (Interphase, Prophase, Prometaphase, Metaphase, Anaphase, Telophase, Cytokinesis).
• Key phases can be identified by characteristics (e.g., anaphase has chromatids moving apart).

Mitosis is vital for forming all the cells in the body and ensuring genetic consistency during cell division.