Specialisation

• What happens during tissue culture?

  1. Small pieces of the main plant ie explants are taken
  2. They are sterilised and placed on an agar plate, containing nutrients and growth hormones ie auxins.
  3. The cells divide to form a mass of undifferentiated cells called a callus.
  4. The embyros develop into plantlets that are genetically identical clones.
• How would you use plant tissue culture techniques to show totipotency in seedlings?

  1. Collect explants of the main plant.
  2. Grow them on an agar medium containing nutrients and plant hormones ie auxins.
  3. Use aseptic techniques to prevent contamination ie covering the lid of the dish.
  4. Supply plenty of light and leave for 2 weeks, checking on them.
  5. Look for new leaves to show new plants being formed- plantlets
• Why are stem cells seen as useful?

  They allow tissues and organs to regenerate, which can allow diseases ie diabetes type 1 to be treated by replacing damaged organs with new ones made by stem cells.
• What are some risks of using embryonic stem cells?

  • can be rejected by the receiver's immune system
  • can lead to cancerous cells due to them dividing rapidly
  • can transfer a communicable disease or a genetic disorder from the donor
  • recipient has to take immunosuppresants for their whole life.
• Why is it better to use stem cells from the same person?

  Less risk of rejection because they are genetically identical to the cells.

  • no need for immunosuppressants
• Why are people against the use of embryonic stem cells?

  • destroys embryos
  • embryo has potential to become human life
  • religious/ ethical objections
• What are induced pluripotent stem cells?

  Adult stem cells that have been reprogrammed to express genes that were previously switched off during differentiation by using hormones and enzymes.

  • they can differentiate into any type of cell
  • no destruction of an embryo
  • lower chance of rejection- derived from the patient's blood
  • however, can become cancerous due to rapid dividing.
• What is the role of the Human Fertilisation and Embryology Authority (HFEA)?


  To regulate the use of embryos through consideration of ethical/ legal aspects.

  • an example of an ethical consideration- regard for potential human life.
  • To ensure that the source of the stem cells is acceptable
  • To stop the cloning of humans
  • To consider the maximum age allowed to use embryos for research
• How do cells differentiate to become specialised tissues?

  1. A chemical stimulus ie a protein/ hormone are released.
  2. Some genes are active
  3. Active genes make mRNA
  4. mRNA is translated to produce a protein/ polypeptide.
  5. Cell structure/ function is determined, leading to a specialised cell.
• What are pluripotent cells?

  Can differentiate into many cell types however genes are inactivated so can't differentiate into ALL cell types