Stem cellsIB MYP Biology: Subtopic test

1. 1
   A developmental biologist in Kyoto is watching a fertilised human egg divide by mitosis. In the first few days the cells in the ball of cells look identical and can still become any type of cell. Later, cells in the same embryo become nerve cells, muscle cells and skin cells, each with a different structure.

   (a)

   What name is given to the process by which an unspecialised cell becomes a specialised cell with a particular structure and function?

   [1 mark]

   • AFertilisation
   • BDifferentiation
   • CDiffusion
   • DRespiration

   (b)

   Which statement describes a stem cell?

   [1 mark]

   • AIt is a specialised cell that can no longer divide
   • BIt is a cell that has lost its genetic information
   • CIt is a cell found only in adults
   • DIt is an unspecialised cell that can divide and can become specialised

   (c)

   Outline what is meant by differentiation, using one named example.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A horticulturist in Nairobi grows roses to export. To produce thousands of identical, disease-free plants, she cuts tiny pieces of tissue from the tips of growing shoots and roots, places them on nutrient jelly and waits for new plants to grow.

   (a)

   In which part of a plant are meristem stem cells found?

   [1 mark]

   • AThe tips of the roots and shoots
   • BThe surface of the leaves only
   • CThe dead xylem vessels
   • DThe petals of the flower

   (b)

   Which statement about plant meristem stem cells is correct?

   [1 mark]

   • AThey can only be found in the seed and are lost after germination
   • BThey can only become cells of the same type as their neighbours
   • CThey can differentiate into any type of plant cell throughout the life of the plant
   • DThey are unable to divide by mitosis

   (c)

   Explain why the horticulturist takes tissue from the shoot tips rather than from a mature leaf.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A nine-year-old boy in Dubai has leukaemia, a cancer of the white blood cells. Doctors destroy his diseased bone marrow with chemotherapy and then give him a transplant of bone marrow from his healthy sister. Her bone marrow contains adult stem cells.

   (a)

   Explain how the transplanted bone marrow helps the boy to recover.

   [3 marks]

   (b)

   Compare adult stem cells with embryonic stem cells.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Researchers at an eye hospital in Mumbai tested a treatment for burn damage to the cornea, which can cause blindness. They took a few adult stem cells from the healthy eye of each patient, grew them in the laboratory and transplanted them onto the damaged eye. In a trial, 200 patients with similar corneal damage were allocated at random to two groups of 100. Group 1 had the stem cell transplant and Group 2 had the standard treatment of eye drops. After 12 months, 82 patients in Group 1 had regained useful vision, compared with 41 patients in Group 2. Two patients in Group 1 developed an eye infection and no patient developed a tumour.

   (a)

   Evaluate the trial and state whether its results support the hypothesis that adult stem cell transplants repair damaged corneas.

   [6 marks]

   (b)

   Some people support stem cell research and some object to it. Discuss the benefits and risks of using stem cells in medicine and give a justified conclusion about whether such treatments should be developed.

   [6 marks]

   Total for question 4: 12 marks

End of questions