1.2.3 Stem cells

• What is a stem cell?

  An undifferentiated cell which can:

  1. Give rise to many more cells of the same type

  2. Differentiate into certain other cells
• Describe the two types of animal stem cells

  
  

  Embryonic stem cells

  
  

  ● Found in early embryos, can

  differentiate into any type of body cell

  
  

  Adult stem cells

  
  

  ● Eg. found in bone marrow

  ● Can differentiate into many (not all)

  types of cell, eg. blood cells
• What are the potential uses of stem cells in medicine?

  Embryonic stem cells

  ● Can be cloned and made to differentiate into most cell types

  ● Transplanted into patient to replace faulty / damaged cells

  ● Could treat (Type 1) diabetes (replace pancreas cells) and

  paralysis (replace nerve cells)

  Adult stem cells

  ● Can only differentiate into some cell types

  ● So can treat a smaller variety of diseases eg. bone marrow

  transplant for blood cancer
• What is therapeutic cloning?

  ● Producing embryo with same genes as a patient (transfer patient cell nucleus to empty donor egg cell)

  
  

  ● Stem cells from embryo stimulated to divide to form any cells patient needs for medical treatment
• Describe stem cells in plants

  ● Found in meristem regions (growing regions) in roots and shoot tips

  ● Can differentiate into any type of plant cell, throughout a plant’s lifetime eg. xylem / phloem
• How can stem cells from meristems in plants be used?

  To produce clones of plants quickly and economically, for example:

  ● Rare species to protect from extinction

  ● Crop plants with special features eg. disease resistance → large numbers of identical plants for farmers
• What are some issues associated with the use of stem cells in medicine?

  ● Transfer of viral infection

  ● Risk of rejection by immune system → have to take immunosuppressant drugs

  ● Ethical and religious objections eg. potential life destroyed / embryo cannot give consent
• why is this statement wrong

  “Stem cells are found in the stem of plants.”

  They are found in the root and shoot tips.
• Explain how a transplant of bone

  marrow stem cells can treat

  medical conditions. (2)

  ● Cells differentiate into many / other types of (named) cell

  ● So will cure diseases where cells are damaged / new cells

  needed / eg. paralysis / diabetes / blood cancers
• Advantages of using stem cells from embryos:

  • Can treat a wider variety of diseases as they can differentiate into any type of cell
  • Can create many embryos in a lab
  • Conclusion: The potential of embryonic stem cells to treat more diseases and relieve human suffering makes them a better option.
• Advantages of using stem cells from a patient's own bone marrow:

  • No ethical issues as the patient can give permission, whereas embryos cannot consent and a potential life is destroyed
  • More reliable and a tried and tested technique
  • Procedure is (relatively) safe and doesn't kill the donor
• Give two advantages of using stem

  cells made from a person’s own

  cells, over embryonic stem cells. (2)

  ● Cells will not be rejected

  ● Adult can give consent

  ● No risk of damage to embryo / no (potential) life destroyed
• Suggest two disadvantages of

  therapeutic cloning. (2)

  ● Potential life is destroyed

  ● Shortage of egg donors

  ● Egg collection has risks

  ● Do not yet know risks / side effects of procedure on patient

  ● May transfer (viral) infection

  ● Poor success rate (to produce viable eggs / embryo)
• What is a stem cell?

  An undifferentiated cell which can:

  1. Give rise to many more cells of the same type

  2. Differentiate into certain other cells
• What is the key advantage of therapeutic cloning?

  Stem cells unlikely to be rejected by patient’s immune system