Lecture Notes: Mitosis and Cell Division

Introduction to Mitosis

• Mitosis: Process of cell division resulting in two diploid cells.
• Diploid Cells: Cells with a full complement of chromosomes (2N).
• Mitosis refers to the replication of the genetic material and nucleus.
• Cytokinesis: Process where the cytoplasm divides into two cells.

Interphase

• Interphase: Phase where cell performs its normal functions before mitosis.
  • G1 Phase: Cell growth and accumulation of materials.
  • S Phase: Chromosome replication.
  • G2 Phase: Additional cell growth.
• Chromatin Form: DNA is not tightly wound during interphase.
• Centrosomes: Structures that replicate during interphase; help in cell division later.

Stages of Mitosis

1. Prophase

• Prophase: First stage of mitosis.
  • Chromatin condenses into visible chromosomes.
  • Centrosomes: Begin forming microtubules.
  • Nuclear Envelope: Starts to disassemble.
  • Late Prophase/Prometaphase: Microtubules attach to chromosomes at the centromeres.

2. Metaphase

• Metaphase: Chromosomes align at the center of the cell.
• Kinetochore: Protein structure where microtubules attach.

3. Anaphase

• Anaphase: Sister chromatids are pulled apart to opposite sides of the cell.
• Chromosomes: Each now referred as separate chromosomes.

4. Telophase

• Telophase: Nuclear membranes form around each set of chromosomes.

Cytokinesis

• Cytokinesis: Division of the cytoplasm to form two separate cells.
  • Cleavage Furrow: Indentation that deepens until the cell splits.

Summary and Recycling

• After mitosis, each cell re-enters interphase and prepares for the next cycle of mitosis.
  • G1 → S → G2 → Mitosis

Key Terminologies

• Mitosis: Division of the nucleus.
• Cytokinesis: Division of the cytoplasm.
• Chromatin: Unwound DNA in the nucleus.
• Centrosomes: Organelles that help in organizing microtubules in cell division.
• Centrioles: Structures inside centrosomes.
• Centromeres: Regions where sister chromatids are attached.
• Kinetochore: Protein structure on centromeres where microtubules attach.
• Microtubules: Structural components that assist in cell division.

Visuals and Diagrams

• Diagrams of each phase can help in visualizing the processes.
• Diagrams showing chromatin and chromosomal structures.