Stem cells

• Stem cell - an undifferentiated cell which can differentiate to have different functions
• Cell differentiation - the process where a cell becomes specialised to a function
• Types of stem cells:

  • Embryonic
  • Adult stem cells
  • Meristems
• Embryonic

  • forms when an egg and sperm cell fuse to form a zygote
  • can differentiate into any type of cell in the body
  • scientists can clone these and direct them to differentiate into almost any cell
  • can be used to replace insulin producing cells in patients with diabetes, new neural cells for diseases such as Alzheimers, or nerve cells fro those paralyzed with spinal cord injures
• Adult stem cells

  • found in bone marrow
  • can differentiate into any cell in tissue or organ that they reside in
• Meristmes

  • found in roots and shoot tips
  • can differentiate into any of plant cell, and can be done throughout the life of the plant
  • they can be used to make clones of plants, which may be necessary if the parent plant has a certain desirable feature (such as disease resistance)
  • can be used for research or to save a rare plant from extinction
• Therapeutic cloning - involves an embryo being created with the same genetic material as the patient
• Therapeutic cloning:

  • embryo produced can be harvested to obtain embryonic stem cells
  • these can be grown into any cells the patient needs
  • advantage of this is that they wouldn't be rejected as they would have the same genetic make-up
• Benefits of using stem cells:

  • can be used to replace damaged or diseased body parts
  • unwanted embryos from fertility clinics can be used, as they would be discarded instead
  • allows research to be done into the differentiation process
• Problems with using stem cells:

  • scientists don't fully understand the process of differeniation, so it is hard to control which function cells will take on
  • removal of stem cell destroys embryo
  • people may have ethical or religious objections as it is seen as interference with natural process
  • if growing stem cells are contaminated with a virus, an infection can be transferred to patient
  • money and time could be better spent into other areas of medicine
  • very expensive
• Advantage of of cloning plants using meristem stem cells;

  • Can prevent extinction of rare plants
  • Can produce large numbers of plants which have favourable characteristic
  • Can produce identical copies for research