Stem Cells

• undifferentiated cells, able to continually divide to specialise (differentiate)

Types

• totipotent - divide into ANY/TOTAL types of cell

  • can specialise into placenta cell

  • during early embryonic development - only translate part of their DNA (cell specialisation)

• pluripotent - divide into MOST types of cell

  • cannot specialise into placenta cell

  • during embryonic development up to 16 days

  • often used in research e.g. to replace diabetic beta cells (don’t create insulin), damaged cells, Parkinson disease neurones - not currently used as there are issues (stem cells continually divide to create tumours)

• multipotent - divide into MULTIPLE types of cell

  • found in the bone marrow (adult), umbilical cord blood and placenta

• unipotent - divide into SINGLE type of cell

Induced pluripotent stem cells (iPS)

• produced from adult somatic cells using protein transcription factors (overcomes some of the ethical issues)

  • use any adult body cells

  • manipulate DNA in cells via appropriate transcription factors (molecules that promote or inhibit the transcription of specific genes)

  • ‘return to state of pluripotency’

• very similar to blastocyst stem cells

• self-renewal properties