Syllabus Edition

First teaching 2023

First exams 2025

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Genetic Technology Applied to Medicine (CIE A Level Biology)

Exam Questions

1 hour8 questions
1a
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2 marks

The production of proteins to benefit humans using recombinant DNA technology utilises cells from both prokaryotic and from eukaryotic organisms.

Explain why the production of such proteins is usually carried out by eukaryotic cells, such as yeasts or animal cells in culture, rather than by prokaryotic cells. 

1b
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3 marks

State three advantages of using genetic engineering to produce recombinant human proteins.

1c
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3 marks

Column 1 of Fig. 1 shows three separate human proteins that have been produced successfully using genetic modification of a separate organism. f3~9LX_f_cie-ial-19-2-q1c-e---sq

Fig. 1

Join one of the boxes from Column 1 to the most appropriate box in Column 2 with a straight line.

Do the same linking the boxes in Columns 2 and 3. 

1d
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2 marks

Prior to the use of transgenic organisms to produce insulin, diabetic patients were often given injections of insulin extracted from the pancreases of pigs or cows.

State two advantages of treating diabetics with recombinant insulin over the use of animal-extracted insulin.

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2a
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2 marks

Fig. 1 below shows a representation of a gene probe.

4-1

Fig. 1

Identify the part of the probe in Fig. 1 labelled X and describe its role.

2b
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1 mark

DNA probes are used to test for the presence of a particular allele. The DNA being tested is split into separate strands and the probe in Fig. 1 will bind to the complementary base sequence on the DNA strand.

State the name of this binding process.

2c
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3 marks

A patient decided to undergo genetic screening for a particular inherited condition.

Describe the process of genetic screening.

2d
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2 marks
The offer of a genetic screening test is often accompanied by genetic counselling.

Give two reasons why a patient might choose to receive genetic counselling.

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3a
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2 marks

Name two techniques that can be used to obtain cells from a growing foetus in order for that foetus to undergo genetic screening.

3b
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1 mark

One of the main problems of finding effective gene therapies is that of gene delivery.

Give one explanation of why gene delivery has been largely difficult to implement.

3c
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2 marks

Some gene therapies are being developed for delivery to patients in vivo, whereas other are delivered ex vivo.

Compare and contrast the terms in vivo and ex vivo in this context.

3d
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2 marks

A couple contemplating whether to have children are concerned about the risk of their child(ren) being born with cystic fibrosis, due to the presence of cases of cystic fibrosis in their extended families in previous generations.

Both would-be parents are non sufferers of cystic fibrosis, which is a recessive condition.

Outline the choices that genetic screening may offer this couple in their family planning considerations. 

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1a4 marks

BRCA1 and BRCA2 are genes that code for proteins involved with the repair of DNA mutations

(i)

State how mutations occur in DNA.

[1]

(ii)

Suggest how mutations in BRCA1 and BRCA2 genes could increase the likelihood of tumour development.

[3]

1b2 marks

Individuals with a family history of breast cancer will often have genetic screening to identify mutations in the BRCA1 and BRCA2 genes.

Outline how genetic screening can reduce the risk of breast cancer in high risk individuals.

1c2 marks

Fig. 1 shows a genetic screening technique.

19-2-fig-2-1
Fig. 1

Use Fig. 1 to suggest how a DNA probe can be used to show the presence of a particular allele.

1d3 marks

Screening for BRCA1 and BRCA2 is carried out in adults, but some other genetic traits are tested for in foetuses prior to birth. In either case the results can bring up difficult decisions and individuals considering or undergoing such screening will often receive help from a genetic counsellor to help them think through ethical and social issues.

Outline the social and ethical issues around genetic screening.

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2a3 marks

Adult haemoglobin is a protein made up of four polypeptide chains; two alpha chains and two beta chains. 

Beta thalassemia is a genetic condition in which a mutation in the gene for the beta chain of adult haemoglobin either reduces or prevents its production.

Suggest three symptoms of beta thalassemia.

2b5 marks

A form of gene therapy is being trialled for use in the treatment of beta thalassemia. The treatment involves harvesting stem cells from the bone marrow of patients before altering them in the lab and infusing the cells back into the patient's body. 

(i)

Describe the stem cells found in bone marrow.

[2]

(ii)

Outline the process by which the stem cells can be altered.

[3]

2c2 marks

One difficulty with carrying out safe and effective gene therapy is of ensuring that any new DNA is inserted into the right part of a patient's DNA.

Suggest why the insertion of DNA in the wrong location could be a problem.

2d3 marks

Give three other concerns related to gene therapy.

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3a4 marks

Adenosine deaminase (ADA) is an enzyme involved with multiple chemical reactions inside cells. One effect of ADA deficiency is a lack of lymphocyte maturation.

Outline how ADA deficiency can lead to severe combined immune deficiency (SCID).

3b4 marks

Treatment options for SCID caused by an ADA deficiency include:

  • Enzyme replacement therapy (ERT), in which patients receive injections of recombinant ADA enzymes.
  • Haemoatopoietic stem cell transplant (HSCT), in which patients receive a bone marrow transplant from a donor.

Complete the table below by suggesting an advantage and a disadvantage of each of these treatment types.

  Advantage Disadvantage
ERT    
HSCT    

3c3 marks

More recent treatment for ADA SCID involves the use of gene therapy.

Describe the process of gene therapy for ADA SCID.

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1a4 marks

Human Factor VIII is a protein required for the process of blood clotting. Recombinant human clotting factor VIII (rhFVIII) can be produced in the kidney or ovary cells of hamsters.

Suggest how rhFVIII can be produced using hamster cells.

1b2 marks

Before the production of rhFVIII, factor VIII protein was extracted from the blood of human donors.

State two advantages of producing rhFVIII rather than extracting factor VIII from human blood.

1c3 marks

Recent research has shown that it is possible to produce rhFVIII using human embryonic kidney (HEK) cells. Scientists believe that this could be advantageous because the post-translational modifications that take place in hamster cells are different to those that occur in human cells. rhVIII produced in human cells would therefore be identical to factor VIII produced by fully developed humans.

(i)

Suggest what might happen to proteins during post-translational modification.

[2]

(ii)

Suggest why it is preferable to produce factor VIII that is identical to that produced by fully developed humans.

[1]

1d3 marks

rhFVIII is essential for the treatment of haemophilia, a genetic condition in which non-functioning factor VIII means that blood does not clot.

Haemophilia is caused by a mutation in a gene located on the X chromosome. The dominant F allele codes for normal factor VIII while the mutated f allele codes for non-functioning factor VIII.

A male with haemophilia has a child with a heterozygous woman. Give the phenotype probabilities for their children.

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2a
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6 marks

The polymerase chain reaction (PCR) is used to produce large quantities of DNA from a very small original sample. The main steps of one PCR method are shown in Fig. 1.

fig4-1-qp-specimen-2022-9700-04

Fig. 1

(i)

Explain why it is necessary to heat the mixture to 95 °C (step 1).

[2]

(ii)

Explain why primers are included in the mixture.

[2]

(iii)

Explain why the enzyme Taq polymerase, rather than any other type of DNA polymerase, is used in PCR.

[2]

2b
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10 marks

The presence of a faulty allele of the gene BRCA2 can lead to an increased chance of developing breast cancer. There are many different faulty alleles of the gene BRCA2.

People who are considered to be at risk of breast cancer may choose to be tested for the presence of these alleles in their genomes.

A microarray can be used to test blood samples for the presence of these alleles. The microarray contains DNA probes for different faulty alleles of the BRCA2 gene.

(i)

State the meaning of the term genome.

 [1]

(ii)

Suggest which type of cell from a blood sample is suitable for testing for the presence of these faulty alleles.

   Give a reason for your choice.

[1]

(iii)

Outline how faulty alleles of the BRCA2 gene can be detected using the microarray.

[4]

(iv)

Outline the advantages of screening for faulty alleles of the BRCA2 gene.

[4]

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3a
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1 mark

Huntington's disease is an inherited condition that affects brain function. It is described as a progressive disease as it gets worse over time. The mutation that causes Huntington's disease involves a DNA segment known as a CAG trinucleotide repeat. Normally, the CAG segment is repeated 10 to 35 times within the gene. In a person who has inherited the allele for Huntington's disease there can be 30 to 180 repeats within the gene. 

Scientists studied the allelic profile of CAG repeats in 65 individuals affected by Huntington's disease. There results are shown in the graph below.cie-ial-19-2-sq-h3a

Fig. 1

Individuals can be tested to see if they have an allele for the gene carrying more than 35 CAG repeats. The scientists suggest that their data can be used to predict the age that the individual will develop Huntington's disease. 

Use the information provided in the question and the graph in Fig. 1 to evaluate this suggestion. 

3b
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3 marks

The allele for Huntington's disease is inherited from parent to offspring. Huntington's disease is always fatal.  

Use the data from the graph in Fig. 1 to suggest why Huntington's is present in the population despite its fatality. 

3c
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4 marks

Huntington's disease is caused by a single faulty gene (HTT) that codes for the protein Huntingtin. The repeated CAG segments leads to the production of an abnormally long version of the huntingtin protein which is cut into smaller, toxic fragments that bind together in neurones called medium spiny neurones, disrupting the normal functions of these cells. In vivo gene therapy has shown promise as a possible treatment for Huntington's disease.

Outline how in vivo gene therapy may be used to treat Huntington's disease. 

3d
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4 marks

A couple are planning to start a family and wants to undergo genetic screening to assess their risk of passing on Huntington's disease to their unborn children.

Discuss the benefits of genetic screening in the context of Huntington's disease.

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