topic 8

• what are stem cells?

  unspecialised cells capable of self-renewal (can divide to replace themelves) and differentiation/specialisation- they can develop into other types of cells
• how are stem cells specialised?

  1.stimulus e.g chemical

  2.causes selective activation of genes- some genes may get activated and others may not e.g muscle cells gene coding for myosin and actin may need to be activated

  3.mRNA only transcribed from active genes - translated on ribosomes to make proteins

  4. these proteins modify cells permanently and determine cell function + structure
• whata are the types of stem cells?

  Totipotent cells

  Pluripotent cells

  multipotent cells

  unipotent cells
• what are Totipotent cells?

  stem cells that can divide into every cell type

  -found in early mammalian embryos
• what are Pluripotent cells?

  • found in embryos
  • can differentiate into most cell type ( every body cells except the cells of the placenta unlike the totipotent cells
• What are Multipotent cells?

  • found in mature mammals(adults)
  • Differentiate into a limited number of cell types e.g blood cells
• what are unipotent cells?

  found in mature ammals

  only differentiate into one cell type e.g Cardiomyocytes
• Stem cells in medicine

  Re-grow damaged tissues in accidents or by disease

  • drug testing
• Induced pluripotent stem cells

  How they are produced

  1. Produced from adult somatic cells (non-pluripotent cells or fibroblasts)

  2. Specific protein transcription factors associated with pluripotency put into cells,

  causing the cell to express genes associated with pluripotency (reprogrammed)

  3. Cells cultured

  4. = Induced pluripotent stem cells

  • Used in medical treatment instead of embryonic cells…

  ✓ No immune rejection as can be made using patient’s own cells

  ✓ Overcome some ethical issues with using embryonic stem cells e.g. no destruction of embryo and adult can give permission
• Evaluate use of stem cells in treating human disorders

  • for- Use of embryonic stem cells

  • Tiny ball of cells, incapable of feeling pain, not equivalent to a human

  • Would otherwise be destroyed (if from infertility treatment which creates more

  than needed)

  • Duty to apply knowledge to relieve human suffering

  Against:

  • Use of embryonic stem cells

  • Embryo is a potential human; should be given rights

  • Scientific

  • Induced pluripotent stem cells – cannot yet reliably reprogramme stem cells

  • Could begin to multiply out of control, and cause tumours