Stem cells

• 1. Humans start when a sperm cell joins with an ovum (fertilisation)
  2. Fertiliser ovum undergoes mitosis and forms a ball of cells called an embryo, overtime the cells continue to undergo mitosis
  3. they also change and begin to form specialised cells (differentiation )
  4. cells in early embryo have not differentiated - these are called embryonic stem cells
• A stem cell is an undifferentiated cell which can give rise to more cells of the same type and can differentiate to form other types of cells
• The stem cells in bone marrow differentiate to form cells found in our body
• bone Marrow transport:

  to treat problems with bone marrow ( leukaemia = caner of bone marrow) the patients existing bone marrow is destroyed using radiation

  The patient then receives a transplant from a donor

  The stem cells in the bone marrow now divide and form new bone marrow, also differentiate and form blood cells
• Problems with bone marrow transplant :

  • donor has to be compatible with the patient or white blood cells produced by donated bone marrow could attack the patients body
  • Risk virus can be passed from donor to patient
• Therapeutic cloning :

  in therapeutic cloning, an embryo is produced with the same gene as the patient

  • Stem cells from the embryo can be transplanted into the patient without being rejected by the patients immune system
  • Once inside patient stem cells can then differentiate to replace cells which have stopped working properly
• therapeutic cloning can be useful for a range of medical conditions such as diabetes or paralysis
• Roots and buds contain meristem tissue. these stem cells can differentiate into any type of plant tissue, at any point the life of the plant
• We can clone a rare plant to stop it from going extinct