Mitosis Overview for Leaving Cert

Cell Continuity

• Concept: All cells arise from pre-existing similar cells (Rudolf Virchow's theory).
• Example: Cheek cells arise from other cheek cells.

What is Mitosis?

• A form of nuclear division.
• One parent nucleus divides to form two identical daughter nuclei.
• Importance: Ensures identical genetic material (same DNA) in daughter nuclei.

Chromosome Structure

• DNA coiled around histone proteins forms chromosomes.
• Centromere: Special region with repeated DNA sequences, crucial in mitosis.
• Sister Chromatids: Two copies of each chromosome necessary for mitosis.

Cell Cycle and Mitosis

• Interphase: Longest part; normal cell processes.
  • End of interphase: Preparation for mitosis.
• Mitosis Phase: Followed by cytokinesis (cell division).

Interphase Preparations

• DNA duplication ensures two copies.
• Organelle replication (mitochondria, chloroplasts).
• Increased ATP production for energy.

Stages of Mitosis

1. Prophase
   • Early: Chromosomes condense, centrioles migrate, nuclear membrane breaks down.
   • Late: Chromosomes visible as pairs of sister chromatids, spindle fibers form.
2. Metaphase
   • Chromosomes align at cell's middle, spindle fibers attach to centromeres.
3. Anaphase
   • Chromatids separate into daughter chromosomes, pulled to opposite poles.
4. Telophase
   • Spindle fibers disappear, nuclear membranes form, chromosomes de-condense.

Cytokinesis

• Separation into individual cells.
• Animal Cells: Cytoplasm pinches to form two new cells.
• Plant Cells: Vesicles form cell plate, leading to new cell walls and membranes.

Important Terms

• Haploid: One set of chromosomes (n).
• Diploid: Two sets of chromosomes (2n).

Mitosis vs. Meiosis

• Mitosis: Maintains chromosomal number, produces identical nuclei (growth, repair).
• Meiosis: Reduces chromosomal number (gamete formation), introduces genetic variation.

Cancer and Mitosis

• Uncontrolled mitosis due to genetic mutations.
• Tumors: Mass of cells; benign (localized) vs. malignant (invasive).
• Carcinogens: Agents (e.g., UV radiation, chemicals in smoke) causing cancer.

Key Points

• Remember stages of mitosis: Prophase, Metaphase, Anaphase, Telophase (P.M.A.T).
• Be able to label diagrams and describe each stage briefly.

Additional Notes

• These summaries supplement, not replace, textbooks or teacher guidance.