Lecture Notes: M Phase of the Cell Cycle

Overview of the Cell Cycle

• Interphase: Consists of G1, S, and G2 phases.
• M Phase: Represents cell division, divided into:
  • Mitosis: Division of the nucleus.
  • Cytokinesis: Division of the cytoplasm.

Mitosis

• Mitosis is divided into four phases:
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase

Prophase

• Longest phase of mitosis.
• Chromatin condenses into chromosomes.
• Nucleolus disappears.
• DNA is tightly coiled into sister chromatids.
• Centromeres link sister chromatids.
• Spindle fibers form from centrioles moving to poles.
• Nuclear membrane disappears, allowing spindle fibers to attach to centromeres.

Metaphase

• Centrioles reach poles.
• Spindle fibers align chromosomes along the cell equator.
• Chromosomes aligned end-to-end.

Anaphase

• Spindle fibers separate sister chromatids at centromeres.
• Each chromatid is now a chromosome.
• Chromosomes form a V-shape as they move.
• Chromosomes are drawn to opposite poles (toward centrioles).

Telophase

• Nuclear membrane reforms around chromosome sets.
• Chromosomes disperse back into chromatin.
• Nucleolus becomes visible again.
• Mitosis (nuclear division) is complete.

Cytokinesis

• Division of the cytoplasm.
• Animal Cells: Cell membrane pinches inward to form two daughter cells.
• Plant Cells: Cell plate forms along the equator, leading to cell wall formation and separation.

Key Points

• M Phase: Fourth and final phase of the cell cycle.
• Cell Division: Occurs through mitosis and cytokinesis.
• Mitosis Phases: Prophase, Metaphase, Anaphase, Telophase.
• Results in the formation of two identical daughter cells, identical to the original cell.