Stem cells

• Stem cell

  An undifferentiated cell which can become any type of cell

  
• Undifferentiated

  A cell which is not yet specialised

  
• Differentiated


  A cell which is specialised to a specific function

  
• Human embryo

  A source of stem cells which can become any type of cell

  
• Bone marrow

  A source of stem cells which can become many types of cell including blood cells

  
• Meristem

  The region in plant shoots and roots where mitosis occurs and a source of stem cells in plant tissue

  
• Diabetes

  A disease of the pancreas which may be treated with stem cells

  
• Spinal cord injury

  A cause of paralysis which may be treated with stem cells

  
• Therapeutic cloning

  When an embryo is produced with the same genes as the patient as a source of stem cells

  
• Potential risks of stem cell treatment

  Viral infection, cancer and rejection unless therapeutic cloning is used
• Cloning rare plant species

  A way of protecting plant species from extinction, using meristem tissue
• Cloning disease resistant crops

  A way of providing food security, using meristem tissue
• Zygote


  A fertilised egg cell which divides to form an embryo

  
• Ethical objections

  Moral reasons people may be against stem cell treatments
• Religious objections

  Religious reasons people may be against stem cell treatments
• Advantages of bone marrow stem cells

  Can treat many blood-linked or immune-linked diseases, less ethical concerns than embryonic stem cells, bone marrow is easier to obtain than embryonic cells

  
• Advantages of embryonic stem cells

  No consent required, obtainable via embryos discarded in IVF, can be used to make any type of cell, less risk of rejection if used via therapeutic cloning

  
• Disadvantages of bone marrow stem cells

  Requires voluntary donors, bone marrow extraction can cause pain to an individual and requires consent, may have a risk of infection, can only form cells such as blood cells, risk of rejection

  
• Disadvantages of embryonic stem cells

  Ethical considerations such as potential loss of life or harm to embryo, less easily obtainable than bone marrow stem cells, risk of rejection

  
• Stem cell

  An undifferentiated cell which can give rise to more cells of the same type and can differentiate into other types of cells
• Fertilization

  1. Sperm cell joins with ovum

  2. Fertilized ovum undergoes mitosis

  3. Forms a ball of cells called an embryo

  4. Cells continue to undergo mitosis and begin to form specialized cells

  5. Process of differentiation
• Embryonic stem cells

  • Cells in early stage embryo that have not differentiated and are capable of differentiating into any type of body cell
• Adult stem cells

  • Stem cells found in adult organisms that cannot differentiate into any other type of cell, e.g. bone marrow stem cells
• Bone marrow transplant

  1. Patient's existing bone marrow is destroyed

  2. Patient receives transplant of bone marrow from donor

  3. Stem cells in bone marrow divide and form new bone marrow and blood cells
• Problems with bone marrow transplants

  • Donors must be compatible with patient
  • Risk of viruses being passed from donor to patient
• Therapeutic cloning

  1. Embryo is produced with same genes as patient

  2. Stem cells from embryo can be transplanted into patient without being rejected

  3. Stem cells can then differentiate to replace cells that have stopped working correctly
• Therapeutic cloning could be useful for a range of medical conditions such as diabetes or paralysis
• Some people have ethical or religious objections to therapeutic cloning procedure
• Plant stem cells

  • Found in meristem tissue at root tips and buds
  • Can differentiate into any type of plant tissue at any point in plant's life
• Using plant stem cells


  Can be used to quickly and cheaply clone rare plants or produce cloned crop plants