1. 1
   A fertility clinic uses spare embryos, donated with consent, to grow embryonic stem cell lines in the laboratory. Scientists then attempt to make these cells develop into different specialised cell types by changing the growth conditions.

   (a)

   (a) Which term best describes embryonic stem cells?

   [1 mark]

   • ATotipotent cells that can only become blood cells
   • BPluripotent cells that can differentiate into almost any type of body cell
   • CFully differentiated cells that cannot change type
   • DCells found only in adult bone marrow

   (b)

   (b) The scientists want to grow the stem cells into nerve cells for research into spinal injury. Which of the following is the main scientific reason this is possible using embryonic stem cells but would not be possible using cells taken from an adult's skin?

   [1 mark]

   • ASkin cells have already differentiated and normally cannot change into a different specialised cell type
   • BSkin cells contain a different genome to nerve cells
   • CSkin cells divide by meiosis rather than mitosis
   • DSkin cells are prokaryotic and lack a nucleus

   (c)

   (c) Some members of the public have objected to this research because it involves the destruction of a human embryo. Discuss one ethical concern and one potential medical benefit of using embryonic stem cells in this way.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A gardener takes a small cutting from the tip of a healthy tomato plant shoot and places it in water. After two weeks, the cutting has grown new roots and can be planted in soil to grow into a complete new tomato plant. The gardener explains that this works because of a group of unspecialised cells found at the tip of the shoot.

   (a)

   Which type of tissue contains the unspecialised cells found at the tip of the shoot?

   [1 mark]

   • APalisade mesophyll tissue
   • BXylem tissue
   • CPhloem tissue
   • DMeristem tissue

   (b)

   (b) The new tomato plant grown from the cutting is genetically identical to the parent plant. Which process produced this new plant?

   [1 mark]

   • ASexual reproduction, producing genetic variation
   • BMeiosis, producing genetically different gametes
   • CAsexual reproduction by mitosis, producing a clone of the parent
   • DFertilisation between two gametes

   (c)

   (c) Explain how the unspecialised cells at the tip of the shoot are able to produce the different specialised cell types, such as root hair cells and xylem cells, needed to form a complete new plant.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A hospital treats a patient with a blood disorder using a stem cell transplant. Adult stem cells are collected from the bone marrow of a matched donor and infused into the patient. Over several weeks, the donor stem cells settle in the patient's bone marrow and begin producing new blood cells.

   (a)

   (a) Explain why adult bone marrow stem cells are able to replace the patient's damaged blood cells, but could not be used to grow a replacement liver cell.

   [3 marks]

   (b)

   (b) The donor was carefully matched to the patient before the transplant took place. Suggest and explain two reasons why using a matched donor, rather than an unmatched donor, is important for the success of this treatment.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A government health agency is deciding whether to fund a new national research programme into embryonic stem cell therapies. The programme would use embryos donated from fertility clinics to develop treatments for conditions such as paralysis, diabetes and heart damage. A separate proposal recommends funding research into induced pluripotent stem cells instead, which are made by reprogramming adult body cells so they behave like embryonic stem cells, without requiring an embryo.

   (a)

   (a) Evaluate the potential medical benefits and risks of funding research into embryonic stem cell therapies, compared with continuing to rely only on currently available adult stem cell treatments.

   [6 marks]

   (b)

   (b) Discuss the ethical issues raised by using embryonic stem cells in this research programme, and explain why the alternative proposal to use induced pluripotent stem cells might be seen as more acceptable by some members of the public.

   [6 marks]

   Total for question 4: 12 marks

End of questions