1.2 Cell division

• Chromosomes


  DNA molecules found in the nucleus of a cell
• Chromosomes


  • Carry a large amount of genes that determine characteristics
  • Usually found in pairs
• Mitosis and the cell cycle

  1. Cell grows bigger/increases in mass

  2. Chromosomes replicate to form 2 copies of the same genetic material

  3. Subcellular organelles/structures increase

  4. Nucleus divides with chromosomes pulled to opposite sides

  5. Full cell division with subcellular structures splitting into two
• Use of new cells


  Growth, replace worn out tissue, repair damaged tissue
• Asexual reproduction


  In some plants/animals
• New cells


  Identical to parent cell to carry out same job
• Mitosis


  A form of cell division
• Stem cells


  Unspecialised/undifferentiated cells that can change to form many types of body/plant cells
• Types of stem cells


  • Embryonic stem cells
  • Adult stem cells
  • Meristems (plant stem cells)
• Embryonic stem cells


  Form when egg and sperm fuse to create zygote, can differentiate into any cell in the body
• Adult stem cells


  Found in bone marrow, can only change into a few cell types
• Meristems (plant stem cells)


  Found in root/shoot tips, can change into any plant, can clone themselves by mitosis, ability can last whole life span
• Uses of stem cells


  • Treat diabetes/paralysis
  • Replace faulty blood cells
  • Produce disease resistant plants/preserve rare species
  • Therapeutic cloning to produce stem cells with same genetic material as patient
• Risks of using stem cells in medicine include transfer of infection, ethical/religious objections, and rejection by the body