Gene Technologies (A Level only) (AQA A Level Biology)

Exam Questions

3 hours15 questions
1a1 mark

The genetic code can be described as universal.

Explain the meaning of this.

1b2 marks

The universal nature of the genetic code as described in part a) is extremely useful in recombinant DNA technology (also known as genetic engineering).

Part of the genetic engineering process is shown in Figure 1 below.

 Figure 1

screenshot-2023-07-08-at-6-46-59-am

The enzymes used at the locations marked X in Figure 1 are known as restriction endonucleases.

Explain why restriction endonucleases are useful in the process shown in Figure 1.

1c1 mark

Name another enzyme that would be needed to finish inserting the gene of interest into the plasmid vector shown in Figure 1.

1d2 marks

Restriction endonucleases are one way of obtaining fragments of DNA for research. Another method is to use an enzyme called reverse transcriptase which produces DNA fragments, known specifically as cDNA.

Describe how reverse transcriptase enzymes can be used to produce cDNA.

Did this page help you?

2a1 mark

Figure 1 below shows the process of the polymerase chain reaction (PCR).

 Figure 1

qwDYGvPK_2

State the purpose of PCR.

2b3 marks

State and explain the purpose of the following molecules/substances in the thermocycler shown in Figure 1.

                                     Primers _____

                           Buffer solution _____

                Free DNA nucleotides _____

2c2 marks

State and explain what is taking place at the point marked X in Figure 1.

2d1 mark

Taq polymerase is a DNA polymerase enzyme usually found in the cells of the thermophilic bacterium Thermus aquaticus.

State why Taq polymerase is the enzyme used in the elongation stage of the PCR cycle.

Did this page help you?

3a1 mark

DNA fragments can be cloned using either an in vitro method (PCR) or an in vivo method. Figure 1 below shows the stages involved in cloning DNA in vivo.

 Figure 1

T3z-3R6j_3

 

Stage 1 in Figure 1 shows two methods that can be used to create DNA fragments.

Give one other method that can be used to create DNA fragments

3b1 mark

Stage 5 in Figure 1 shows that it is necessary to identify the transformed cells.    

Define the term transformed in this context.

3c3 marks

Describe how transformed cells can be identified.

3d2 marks

The process of in vivo gene cloning is the same as that used to create recombinant bacteria by genetic engineering.

Give two examples of applications of recombinant DNA technology.

Did this page help you?

4a2 marks

Figure 1 below shows a representation of a gene probe.

 Figure 1

Ft~BcrZY_4

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

4b1 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 Figure 1 will bind to the complementary base sequence on the DNA strand.

State the name of this binding process.

4c3 marks

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

Describe the process of genetic screening.

4d2 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.

Did this page help you?

5a1 mark

Figure 1 below shows the result from a genetic fingerprinting (also known as genetic profiling) test using gel electrophoresis.

Figure 1

e7Vtfh~6_5

Genetic fingerprints use sections of DNA known as variable number tandem repeats (VNTRs); short sequences of repeated bases found within non-coding sections of DNA.

State why VNTRs are useful for carrying out genetic fingerprints like that shown in Figure 1.

5b2 marks

After being cut into fragments, DNA is initially placed into the wells at the top of the gel in Figure 1, before the electrodes, represented by (-) and (+), are switched on. The DNA bands show the final position of DNA fragments after a specified amount of time has passed.

Explain why DNA fragments travel through the gel, and why they appear as bands at different positions.

5c2 marks

The wells in Figure 1 are labelled CS (crime scene) and 1, 2, and 3, for three different suspects who may or may not have been present at the crime scene.

Identify which of the suspects is likely to have been present at the crime scene. Explain your answer.

5d2 marks

Other than in crime scene investigations, give two other applications of genetic fingerprinting techniques.

Did this page help you?

1a2 marks

Seven skeletons were discovered in a house in Pompeii, three of which were children. It is believed they were inhabitants and workers within the house when Mount Vesuvius erupted on 24 October 79 AD. Researchers were able to isolate very small amounts of  DNA from these skeletons. The DNA obtained was used in the polymerase chain reaction (PCR). Genetic fingerprinting was then carried out on this DNA to identify the skeletons.

Figure 1 shows some of the results of the genetic fingerprinting of the three children and four adults.

Figure 10

Explain why the researchers used polymerase chain reaction in their investigation.

1b4 marks

During the polymerase chain reaction method, DNA is heated to 94 °C and DNA primers, nucleotides and enzymes are added to the mixture.

(i)
Explain why the DNA is heated to 94 °C.

(ii)
Describe what is meant by DNA primers and explain why these are added during the polymerase chain reaction.

(iii)
State why the enzymes used in the polymerase chain reaction must be thermostable.
1c2 marks

It was determined that the three children were siblings and shared the same biological parents. Their mother is Adult B.

Suggest which of the other adults is the children’s father and give the reason for your answer.

1d6 marks

Describe the method by which genetic fingerprinting is undertaken.

Did this page help you?

2a5 marks

Spinocerebellar Ataxia is a genetic condition that leads to a loss in the brain’s ability to coordinate the movement of hands, eye and in speech. The gene involved contains a section of DNA with many repeats of the base sequence CAG. The number of these repeats determines whether or not an allele of this gene will cause Spinocerebellar Ataxia.

Figure 1 shows the age at which a sample of patients with Spinocerebellar Ataxia first developed symptoms and the number of CAG repeats in the allele causing Spinocerebellar Ataxia in each patient.

Figure 1

3hZ_HDw1_1

People can be tested to determine the number of CAG repeats on this allele. Some scientists suggest that the results in Figure 1 can be used to predict whether an individual will develop Spinocerebellar Ataxia and at what age.

Use the information in Figure 1 to evaluate this suggestion.

2b2 marks

Using the information in Figure 1, suggest why the allele that causes Spinocerebellar Ataxia is passed on in human populations despite the condition being fatal.

2c1 mark

DNA samples were taken from four people, W, X, Y and Z. Polymerase chain reaction (PCR) was used to produce many copies of the section of DNA containing CAG repeats obtained from each person. The DNA fragments were then separated by gel electrophoresis and detected by a radioactively labelled probe. Figure 2 shows the appearance of part of the gel after an X-ray was taken. The bands show the DNA fragments that contain the CAG repeats.

Figure 2

2-1

Each individual usually has two bands. Suggest why only one band was seen for Person X.

2d2 marks

Only one of the four people (W, X, Y and Z) tested positive for Spinocerebellar Ataxia.

Suggest which person this was and explain your answer.

Did this page help you?

3a2 marks

A scientist used a restriction enzyme to cut a section of mouse DNA into multiple pieces.The enzyme produced a staggered cut. A scientist wanted to insert these pieces of DNA into plasmids and used the same restriction enzyme to cut the plasmids.
Explain why the pieces of mouse DNA would be able to join to the cut DNA of the plasmids.

3b2 marks

Name the other enzyme the scientist added to the mixture to form recombinant plasmids and describe its function.

3c2 marks

The plasmid formed from this experiment is used as a vector. Define the term vector when used in this context.

3d2 marks

Before choosing a plasmid to use, the scientists ensured it contained antibiotic resistance genes.

Explain the reason for this.

Did this page help you?

4a2 marks

Farmers use genetic engineering to quickly introduce genes that benefit the health and value of their livestock. Protein Q is a protein that gives pigs resistance to a disease that is killing livestock. Goats can be genetically engineered to produce Protein Q in their milk.

Figure 1 shows the stages involved in this process.

Figure 1

0qNy5N5a_3

The zebrafish gene attached to the pig Protein Q gene codes for a protein that glows blue under fluorescent light. Explain why this gene has been attached.

4b3 marks

State the role of a promoter and suggest why a goat promoter specific to the milk gland was used instead of a pig promoter.

4c2 marks

There are very few live births that result from the multiple embryos that are implanted.The likelihood of producing offspring from genetically modified eggs is low. Suggest one reason why few live births result from the many embryos that are implanted.

4d1 mark

When pigs are bred in farms, it is important to ensure only unrelated pigs breed. Suggest how genetic fingerprints might be used to do this.

Did this page help you?

5a2 marks

A researcher wants to detect and measure accurately the amount of RNA present in a liver tissue sample in order to determine the types of proteins being expressed. They do this by RT-PCR (reverse transcriptase-polymerase chain reaction).

RT-PCR uses a reaction mixture containing:
  •       the sample for testing
  •       DNA polymerase
  •       primers
  •       reverse transcriptase
  •       DNA nucleotides
  •       fluorescent dye
Explain the roles of DNA polymerase and reverse transcriptase in RT-PCR.
5b2 marks

Before commencing the experiment, the researcher adds hydrolytic enzymes to the sample to ensure all DNA is hydrolysed. Explain why the researcher carries out this step.

5c1 mark

DNA replication eventually stops in the polymerase chain reaction.

Suggest one reason why this is.

5d2 marks

Researchers have used the RT-PCR method to detect the presence of different hepatitis viruses, which are a family of RNA viruses that affect the liver.

Explain why the researchers produced a variety of primers for this procedure.

Did this page help you?

1a3 marks

Salty soils can inhibit the growth of crop plants, such as tomatoes, particularly in coastal areas. Scientists have genetically modified some species of tomato to increase their salt tolerance. Figure 1 shows the process used to introduce a gene for a sodium-pump protein, into the genome of tomato plants. The gene resulted in increased tolerance of the tomato plants to high salt soil, without affecting the taste or salt content of the fruit produced.

Figure 1

9wevze5z_1

Describe three methods that could be used to obtain the DNA fragment which contains the gene for the sodium pump protein.

1b2 marks

In the process shown in Figure 1, the required gene sequence is extracted from Arabidopsis and is inserted into the tomato plant.

Explain why the transgenic tomato plant is able to produce the sodium pump protein despite being a different species to the donor plant.

1c4 marks

Suggest two possible ways that cells with the sodium pump gene might be selected in stage 4 of Figure 1.

1d2 marks

Explain the evidence from Figure 1 that the genetically modified tomato plant cells are totipotent.

Did this page help you?

2a3 marks

q2a-8-4-hard-gene-technologies

Use the information provided above along with your own knowledge to answer the Following.

Suggest and explain how a mutation, such as the Philadelphia mutation, could be acquired later on in life (lines 5-6).

2b3 marks

The BCR-ABL test is available only to patients who have been diagnosed with leukemia (lines 10-11). Suggest how genetic screening may be valuable in the treatment of patients with the philadelphia mutation.

2c6 marks

Outline how scientists could use polymerase chain reaction (PCR) in combination with a labelled gene probe to detect the presence and quantity of the philadelphia fusion gene (lines 14-15).

2d3 marks

Outline the role of a genetic counsellor (line 19-20).

Did this page help you?

3a3 marks

Wild boars are found across many European countries. Scientists studied the genetic diversity of these boar by comparing the variable number tandem repeats (VNTRs) of the mitochondrial DNA. Mutations can cause variation in the mitochondrial VNTRs. Table 1 shows the results of their study.

Table 1

Country

Number of boar sampled

Number of different VNTR in mitochondrial DNA

Poland 79 6
France 97 2
Germany 105 3
Belgium 12 2
Italy 31 2
Croatia 15 5

 

Suggest why differences in VNTR on mitochondrial DNA can be used to establish diversity.

3b6 marks

Explain how genetic fingerprinting could be used to make comparisons between the VNTR sequences in the different boar populations.

3c3 marks

Organisms can protect their own cellular DNA from the action of restriction endonucleases by methylation of the adenine and cytosine.

Use your knowledge of enzyme action to explain this observation

3d2 marks

One restriction enzyme is used to cut a sample of the DNA from the mitochondrial DNA of a wild boar. The resulting genetic fingerprint can be seen in Figure 1.

Figure 1

screenshot-2023-07-08-at-2-28-27-pm

State how many times that enzyme made a cut in the DNA and justify your answer.

Did this page help you?

4a2 marks

Genetic engineering can be used to create insulin for patients suffering from type 1 diabetes. The process involves the use of bacterial vectors in the process shown in Figure 1.

Figure 1

j_Gi4hmr_2

Suggest why bacterial cells are used in the production of human insulin for diabetic patients.

4b3 marks

Explain how antibiotic resistance genes can be used to make sure that the only bacteria which are replicated are those which have taken up the modified plasmids containing the insulin gene.

4c3 marks

Compare the use of in vivo gene cloning compared to in vitro gene cloning for the production of gene fragments.

4d2 marks

Historically, insulin extracted from pigs was used to treat diabetics.

Suggest why it may be more desirable to use modern gene technology methods to produce insulin for diabetic patients rather than using animal insulin.

Did this page help you?

5a3 marks

A plantibody is an antibody which is produced by a plant which has been genetically engineered using an animal gene for a desired antibody.

Suggest how plantibodies could be used to combat disease in humans.

5b6 marks

With reference to the enzymes involved, describe how the antibody gene discussed in part (a) could be isolated from an animal cell and introduced into a crop plant such as maize.

5c3 marks

An alternative way to isolate the required antibody gene sequence is using a gene Machine. When using a gene machine, scientists must consider the biosafety and biosecurity of the sequence being created.

Suggest what is meant by this.

5d6 marks

Evaluate the use of recombinant DNA technology to treat disease.

Did this page help you?