Cell devision notes

  • Cell Division

    • "All cells develop from pre-existing cells."

    • Cell continuity:

    • Yeast cells: budding

    • Bacteria cells: binary fission

    • Rhizopus cells: spores

  • Chromosomes

    • Coiled threads of protein (60%) and DNA (40%).

    • DNA contains genes for genetic make-up.

    • A typical body cell has 46 chromosomes, which must divide to produce new cells.

  • Types of Cells

    • Haploid Cells (n):

    • One set of chromosomes.

    • Sperm and egg cells have 23 chromosomes each.

    • Fertilization forms a diploid (46 chromosomes).

    • Diploid Cells (2n):

    • Two sets of chromosomes.

    • 46 chromosomes for humans; homologous pairs present.

  • Mitosis

    • Nuclear division producing two identical nuclei.

    • Stages:

    1. Prophase: Nuclear membrane breaks down, chromosomes visible.

    2. Metaphase: Chromosomes lined at the equator, spindle fibers attach.

    3. Anaphase: Shortest phase; centromeres split, chromosomes pulled apart.

    4. Telophase: Chromosomes elongate, nuclear membranes reform, cell begins to split.

  • Cell Division in Animals and Plants

    • Animals: Cleavage furrow splits cell at the equator.

    • Plants: Cell plate from vesicles divides the cell, forming a middle lamella.

  • Functions of Mitosis

    • Multi-cellular: Growth and repair

    • Uni-cellular: Asexual reproduction

  • Cancer

    • Disorders from unregulated mitosis.

    • Types:

    • Malignant (e.g., lung cancer)

    • Benign (e.g., warts)

  • Meiosis

    • Nuclear division producing four non-identical haploid nuclei (gametes).

    • Occurs in testes and ovaries, provides genetic variation.

  • Mitosis vs. Meiosis

    • Mitosis: 2 daughter cells, identical, same chromosome number as parent.

    • Meiosis: 4 daughter cells, variations, haploid (half parent chromosome number).