stem cells

• stem cells:

  undifferentiated cells that continually divide and become specialised cells
• totipotent:

  can divide into any type of body cells

  only occurs in the early mammalian embryos

  during development : can translate only one part of DNA - turns specialised
• pluripotent:

  only found in the embryos 

  can become almost any type of cell

  used in research - to treat human disorders (treat damaged cells)

  issues:

  • ethical issues: therapeutic cloning
  • can continually divide to create tumours
• unipotent

  found in mature mammals

  can only differentiate into one type of cell (same type of cell)
• multipotent

  can differentiate into limited number of different cells

  found in the bone marrow
• induced pluripotent stem cells (iPS)

  adult somatic cells DNA manipulated using transcription factors

  • overcomes ethical issues
• advantages of IPS

  • long term
  • won't cause rejection
  • single treatment
  • can divide indefinitely
• how transcription factors can reprogramme cells to form iPS cells.

  • transcription factors attach to gene / DNA / promoter region;
  • Stimulate / inhibit transcription / RNA polymerase;