Applications of recombinant DNA technologyAQA A-Level Biology: Subtopic test

1. 1
   A pharmaceutical company produces human insulin by inserting the human insulin gene into plasmids, which are then taken up by bacteria grown in large fermenters. Before this technology, insulin for people with diabetes was extracted from the pancreases of pigs and cattle.

   (a)

   Which term describes DNA that contains genetic material from two different species?

   [1 mark]

   • AGenomic DNA
   • BRecombinant DNA
   • CMitochondrial DNA
   • DSatellite DNA

   (b)

   The bacteria transcribe and translate the human insulin gene to make human insulin. Which feature of the genetic code makes this possible?

   [1 mark]

   • AIt is degenerate, so there are several codons for each amino acid
   • BIt is non-overlapping, so each base is part of only one codon
   • CIt is universal, so the same triplet codes for the same amino acid in all organisms
   • DIt contains introns that bacteria are able to remove

   (c)

   Suggest two advantages of producing human insulin using recombinant bacteria instead of extracting it from pigs.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A seed company has produced soya plants containing a gene from a bacterium that makes them resistant to a broad-spectrum herbicide. Farmers can spray the herbicide over whole fields to kill weeds without harming the soya crop. Most of the farmers buying the seed run large commercial farms.

   (a)

   The bacterial gene was delivered into the soya cells using a vector. Which could be used as the vector?

   [1 mark]

   • ATaq polymerase
   • BDNA ligase
   • CA restriction endonuclease
   • DA plasmid carrying the herbicide-resistance gene

   (b)

   Which statement is an environmental concern about herbicide-resistant crops?

   [1 mark]

   • AThe resistance gene could spread by pollen to wild relatives, producing herbicide-resistant weeds
   • BThe crop will no longer be able to photosynthesise
   • CPeople who eat the soya will have recombinant DNA in their own cells
   • DSoil bacteria will lose their plasmids

   (c)

   Suggest two reasons why some environmental groups oppose the use of this herbicide-resistant soya.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A child is diagnosed with severe combined immunodeficiency (SCID), caused by a recessive allele that means the enzyme adenosine deaminase is not made, so white blood cells die. In a clinical trial, bone marrow stem cells are removed from each child, a functional allele is inserted into them using a viral vector, and the cells are returned to the child's blood. In the trial, 18 of 20 children recovered a working immune system within three years, but 2 children developed leukaemia because the vector inserted the allele next to a gene controlling cell division.

   (a)

   Describe how gene therapy is used to treat a condition caused by a faulty recessive allele.

   [3 marks]

   (b)

   Using the data, evaluate the use of this gene therapy for children with SCID.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A biotechnology company has developed a drought-tolerant maize that carries a gene from a bacterium. It sells the seed in sub-Saharan Africa, where droughts regularly cause harvest failure. The seed is protected by a patent, so farmers must buy new seed each year instead of saving their own. The company also holds a patent on recombinant blood clotting factor VIII, made by genetically modified mammalian cells and used to treat haemophilia A; treatment costs tens of thousands of pounds per patient each year. Humanitarian charities support the company's work, while some environmental and anti-globalisation groups oppose it.

   (a)

   Evaluate the ethical, financial and social issues raised by the company's use and ownership of the drought-tolerant maize.

   [6 marks]

   (b)

   Haemophilia A is caused by a faulty recessive allele of the factor VIII gene. Evaluate gene therapy compared with regular injections of recombinant factor VIII as a way of treating haemophilia A.

   [6 marks]

   Total for question 4: 12 marks

End of questions