Stem cells

• Stem Cells

  • a stem cell is an undifferentiated or partially undifferentiated cell and therefore can divide by mitosis to give rise to cells that can differentiate into various cell types.
  • properties of self-renewal (replication) and differentiation (potency)
  • this is why, despite all cells having the same DNA and genetic information, they are different (eg muscle cells vs brain cells)
  • most of the genes in any cell are 'switched off'. they are not read and used to make proteins
  • differentiation serve to turn off genes to prevent them from being expressed in a cell or certain genes on
• Types of Stem Cells

  • Totipotent
  • Pluriopotent
  • Multipotent
  • Oligopotent
  • Unipotent
• Totipotent cells:

  • cells that are capable of becoming any kind of cell in an embryo OR an extraembryonic cell (eg a placenta)
  • a cell with the potential to differentiate into either an embryonic stem cell or an extraembryonic cell.
  • zygote and morula are TOTIPOTENT - as they can become ANY kind of cell in an embryo like a blood cell, muscle cell, brain cell etc
• Pluripotent

  • they can only differentiate to become cells in the embryo. they cannot differentiate into extraembryonic cells anymore.
  • can differentiate further via 3 different germ layers of cells
  • Endoderm, Ectoderm, Mesoderm
  • the umbilical cord stem cells, embryonic stem cells are pluripotent
• Multipotent

  • Stem cells that can differentiate into a limited number of specialised cell types belonging to a specific tissue or organ (within their germ layer).
  • these cells are part of either of the 3 germ layers
  • ectoderm, mesoderm and endoderm.
  • the ectoderm forms skin and the nervous system
  • mesoderm forms muscle, bone, and blood and the urogenital
  • endoderm forms lungs and the gastrointestinal tract
  • bone marrow stem cells are multipotent
• Bioethical Consideration of Stem Cell Research

  • Respect
  • zygotes and embryos do not give consent for totipotent and pluripotent research (extracting destroys them)
  • Beneficence
  • Stem cell research could potentially help thousands with currently untreatable diseases/disabilities
  • Non-maleficence
  • harming the zygotes and embryos
  • Justice and Integrity
  • If scientists do achieve results, they must ensure it's accessible to everyone and to publish their work transparently
• Cell Potency and Self-renewal

  • when stem cells go through mitosis, they produce 2 daughter cells. One is genetically identical, the other is a differentiated, specialised cell
  • characteristics that make a cell a stem cell
  • potency - the ability to differentiate
  • high potency - the more cells they can differentiate into
  • self-renewal
  • create a genetically identical daughter cell
• Specialised Cells


  cells that are designed to carry out a particular, 'special' role in the body