Genome sequencing, personalised medicine and GMOsEdexcel A-Level Biology A: Subtopic test

1. 1
   Until the 1980s, insulin for people with diabetes was extracted from the pancreases of pigs and cattle. Today most insulin is made by genetically modified bacteria. The human insulin gene is copied from mRNA and inserted into a plasmid, which is taken up by the bacteria and grown in large fermenters.

   (a)

   Which enzyme is used to cut a plasmid at a specific base sequence so that the insulin gene can be inserted?

   [1 mark]

   • ADNA polymerase
   • BDNA ligase
   • CDNA helicase
   • DRestriction endonuclease

   (b)

   Why is the insulin gene copied from mRNA rather than cut from human chromosomal DNA?

   [1 mark]

   • AThe copy made from mRNA has no introns, which bacteria cannot remove from a transcript
   • BmRNA is more stable than DNA inside the bacterial cell
   • CBacteria can only read RNA and not DNA
   • DHuman DNA is too large to fit in a plasmid

   (c)

   Explain two advantages of using genetically modified bacteria to make human insulin rather than extracting it from pigs.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Warfarin is a drug that prevents blood clots. The dose that is safe varies between patients because of differences in the alleles of genes coding for enzymes that break down the drug. A hospital sequences the genomes of its patients before prescribing, and stores the results on a secure database.

   (a)

   Which statement best defines personalised medicine?

   [1 mark]

   • AGiving every patient the same drug at the same dose
   • BMaking a new drug for each patient from their own cells
   • CChoosing the drug and dose for a patient based on information such as their genotype
   • DAllowing patients to choose any drug they prefer

   (b)

   Which ethical issue is raised most directly by storing the patients' genome sequences on a database?

   [1 mark]

   • AThe warfarin tablets might be too expensive
   • BInsurers or employers might gain access and discriminate against people with certain alleles
   • CThe patients' alleles will mutate when they are sequenced
   • DSequencing will remove the need for informed consent

   (c)

   Suggest how sequencing a patient's genome could reduce the chance of an adverse reaction to warfarin.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A company has genetically modified tobacco plants so that their leaves make a human antibody that is used as a drug. The antibody gene was inserted into the chromosomes of the plant cells. The plants are currently grown in sealed greenhouses, and the company is considering growing them in open fields instead.

   (a)

   Suggest three advantages of producing the antibody in plants, compared with producing it in animals.

   [3 marks]

   (b)

   Evaluate the company's proposal to grow the plants in open fields.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A health service plans (i) to sequence the genomes of its patients so that treatments can be personalised, and (ii) to buy human proteins made by genetically modified organisms, including insulin from bacteria, antithrombin from the milk of genetically modified goats and antibodies from genetically modified plants.

   (a)

   Discuss the social, moral and ethical issues raised by sequencing patients' genomes to personalise treatment.

   [6 marks]

   (b)

   Evaluate the risks and benefits of using genetically modified organisms, such as bacteria, goats and plants, to make drugs.

   [6 marks]

   Total for question 4: 12 marks

End of questions