Stem cells

• Stem cell


  Undifferentiated cell with the ability to continually divide and become specialized
• Types of stem cells

  • Totipotent
  • Pluripotent
  • Multipotent
  • Unipotent
• Totipotent stem cells


  • Can divide into any type of cell in the body
  • Found in the very early stages of an embryo
  • Only available for a limited time
• Pluripotent stem cells


  • Found in the inner mass of a blastocyst
  • Can divide into almost any type of cell, except placental cells
  • Potential for treating human disorders by replacing damaged cells/tissues
• Issues with pluripotent stem cells include potential to form tumours and ethical concerns around therapeutic cloning and destroying embryos
• Multipotent stem cells


  • Can differentiate into a limited number of different cell types
  • Found in bone marrow
• Unipotent stem cells


  • Can only differentiate into the same type of cell
• Sources of stem cells

  • Embryos up to 16 days after fertilization
  • Umbilical cord
  • Placenta
  • Bone marrow
• Induced pluripotent stem (iPS) cells

  • Pluripotent stem cells created from adult somatic cells by manipulating their DNA using transcription factors
  • Overcome ethical issues of using embryonic stem cells
• iPS cells behave similarly to pluripotent stem cells from a blastocyst, with self-renewal properties and ability to divide indefinitely