G e n e t i c s   &   R e p r o d u c t i o n :     L e c t u r e  # 11 Vocabulary | Study Questions
Cell Division: Mitosis & Cytokinesis
Objectives:
  1. Understand the mechanics and phases of cell division.

  2. Understand the significance of mitosis as it relates to growth, repair, replacement, and asexual reproduction.
Cell (nuclear) division occurs as either mitosis or meiosis. The subject of the next lecture, Meiosis involves the production of sex cells. Mitosis occurs at an enormous level: as we sit here, we produce 2-2.5 million RBCs (red blood cells) are being produced mitotically. Cytokinesis is the splitting of the cell. Except for sperm cells and egg cells, ALL cells are produced by mitosis.
  1. The mechanics of cell division
    1. Initiation of cell division
      A cell knows its time to divide when it gets too big; cell division is triggered by cell size. When the cell gets to be a certain size, metabolic activity changes resulting in cell division. So size and, metabolism cooperate in mitosis.
    2. DNA replication
      Before the nucleus can divide the DNA must be replicated.
    3. Division of the DNA (mitosis) and cytoplasm (cytokinesis)
      The same # of chromosomes in the original cell will be found in both daughter cells (the two cells that result from the cell dividing.) Cytokinesis is when the cytoplasm, containing the organelles, divides.
  2. Basic cell division sequence
    11.1 Cell Cycle
    Every cell (including your trillions) are produced following this sequence.
    1. Interphase
      Interphase is NOT a part of mitosis. In this stage the cell is actively growing, metabolizing, etc.. The cell's DNA is replicated while in interphase.
      1. DNA replication
        Yes, in interphase, DNA is making copies of itself.
      2. Transcription and translation
        Yes, in interphase, is when the whole protein synthesis thing is going on.
    2. Prophase
      11.2 Mitosis
      The FIRST mitotic phase: the DNA has been replicated and is tightly coiled.
    3. Metaphase
      The chromosomes line up at the center plate of the cell. The spindle fibers attach to the centromeres of the chromosomes.
    4. Anaphase
      Chromatids separate into chromosomes and move to opposite ends of the cell.
    5. Telophase
      The chromosomes have moved to each side and the nuclear membrane reforms. This is followed by cytokinesis, which results in two daughter cells having been formed, each with a full set of identical chromosomes. (Review the cell cycle. 'G' stands for growth; 'S' for synthesis.)
  3. Significance of mitosis
    11.3 Mitosis: Summary
    All the life you see results from mitosis: the trees, birds, people, you name it.
    1. Growth
      All living, more-than-one-cellular things grow from a single cell into a multicellular organism through the process of mitosis.
    2. Maintenance (repair and replacement)
      Living things continually need to produce new cells for these purposes: to repair and to replace cells. (When we're cut or break bones, or lose skin cells, mitosis is the process we depend upon.)
    3. Asexual reproduction
      Asexual reproduction results in genetically identical cells. (Common in prokayotes and plants; not in animals.)