stem cells 1

• stem cells

  • can divide by mitosis an unlimited number of times
  • can develop into specialised cells- differentiation
• types of potency

  • totipotency= can differentiate into any cell type found in embryo(zygote is totipotent)
  • pluripotency=different into any cell type found in embryo but no cells forming placenta and umbilical cord
  • multipotent=adult stem cells, can differentiate into a limited range of cell types, no longer pluri potent
• stem cells in medicine

  • replace daamged tissues and cells
  • 2 sources of medical stem cells- embryonic and adult
• leukaemia treatment

  • existing stem cells killed before replacing using a bone marrow stem cell replacement
  • will replace all bone marrow cells
• use of embryonic stem cells

  • differentiate into almost all cell types
  • totipotent(3/4 days after fertilisation), pluripotent(taken on day 5)

  uses waste embryos from IVF
• use of adult stem cells

  • can only produce a limited range of cell types
  • bone marrow= different types of blood cells
  • less controversial as doner can give permissions
  • however, closr match needed in terms of blood type and body antigens- less chance of rejection by immune system
• benefits

  • treat wide variety of diseases
  • organs developed from patients own stem cells reduces risk of organ rejection and need to wait for donation
• risk/issues

  • risk of cultured stem cells accumulating mutations that can lead to developing into cancer cells
  • stem cells cultured in lab could be infected with virus
• social issues

  • lack of peer reviewed clinical evidence of the success of stem cell treatments
  • educating public sufficiently about what stem cells are and how they can be used
• ethical issues

  • embryos cannot consent
  • should an embryo be treated as a human with human rights
• cell differentiation

  • under certain conditions/chemical signals, some genes in a stem cell are activated and others inactivated
  • MRNA transcribes activated genes only
  • MRNA then translated for form proteins
  • these proteins are responsible for modifying the cell eg structure
  • cells become specialised
• transcription factors

  • proteins that control transcription of genes by binding to specific regions of DNA
  • activators= help RNA polymerase bind to DNA to begin transcription
  • repressors=stop RNA polymerase binding to DNA to inhibit transcription of gene