Stem Cells

• 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

  5. Cells begin to form specialized cells
• Differentiation


  The process where cells specialize into different cell types
• Embryonic stem cells


  Undifferentiated cells in the early stage embryo that can differentiate into any type of body cell
• Adult stem cells


  Stem cells found in adult organisms that cannot differentiate into any other type of cell
• Adult stem cells


  • Bone marrow stem cells that differentiate into blood cells
• Bone marrow transplant


  1. Patient's bone marrow destroyed

  2. Patient receives transplant of donor bone marrow

  3. Stem cells divide and form new bone marrow

  4. Stem cells differentiate and form blood cells
• Problems with bone marrow transplants

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


  1. Embryo produced with same genes as patient

  2. Stem cells from embryo transplanted into patient

  3. Stem cells differentiate to replace malfunctioning cells
• Therapeutic cloning could be useful for a range of medical conditions
• Some people have ethical or religious objections to therapeutic cloning
• Plant stem cells


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

  1. Clone rare plants to prevent extinction

  2. Produce cloned crop plants resistant to diseases