Stem Cells

• Stem cells


  Undifferentiated cells in an organism that can produce many more cells of the same type, and specialised cells by differentiation
• Stem cells in animals

  • A zygote is a single cell formed when an egg cell and sperm cell join together, which divides to form a ball of cells called an embryo
  • The embryo contains embryonic stem cells, which differentiate to form many different specialised cell types
  • Adult animals retain some stem cells, such as in the bone marrow which contains adult stem cells that form many cell types, including blood cells
• Stem cells in plants

  • The meristems in plants contain stem cells
  • Meristem tissue is found at the tips of roots and shoots, and it differentiates throughout the life of the plant to form root hair cells, xylem, phloem and other cells in the roots and stems/leaves
• Stem cell treatment


  Stem cells may be able to help treat conditions such as diabetes and paralysis by replacing damaged or missing cells in the pancreas or nervous system
• Advantages of embryonic stem cells

  • Easy to extract
  • Can grow embryo
  • Can produce any type of cell
• Disadvantages of embryonic stem cells

  • Embryo destroyed when cells removed
  • Some people think embryo has a right to life
• Advantages of adult stem cells

  • Taken from the person to be treated, so won't cause rejection by the body
• Disadvantages of adult stem cells

  • May not stop dividing and so may cause cancer
  • Risk of viral infection
  • Can only produce a few types of cells
• Clones are genetically identical individuals
• Uses of cloning in plants

  • Saving rare plant species from extinction by producing large numbers
  • Cloning crop plants with useful features like disease resistance to provide large numbers for farmers
• Therapeutic cloning involves replacing the nucleus in an egg cell with the nucleus from one of the patient's cells, then stimulating the egg cell to form an embryo
• Advantages and disadvantages of therapeutic cloning

  • Advantage: Can produce stem cells from patient's own cells
  • Disadvantage: Embryo is destroyed