Genome projects and gene technologiesAQA A-Level Biology: Topic test

20 questions, 54 marks

AQA A-Level Biology

Genome projects and gene technologies topic test

Total 54 marks

Name

Class

Date

1
Scientists have sequenced the whole genome of a bacterium that causes a respiratory disease. From the base sequence they predicted the amino acid sequences of all the proteins that the bacterium can make. Several of these proteins are on the surface of the bacterial cell.
(a)
What is the term for the complete set of proteins that the bacterium can make?
[1 mark]
AGenome
BProteome
CGenotype
DKaryotype
(b)
Which statement explains why the proteome of a bacterium can be predicted from its genome more easily than that of a human?
[1 mark]
ABacterial genomes contain little non-coding DNA and few regulatory genes
BBacteria have more genes than humans
CBacterial DNA is linear, so it is easier to sequence
DBacteria do not use the genetic code
(c)
Explain how knowing the proteome of the bacterium could help scientists to make a vaccine against the disease.
[2 marks]
Total for question 1: 4 marks
2
People with haemophilia A lack functional clotting factor VIII. Scientists make the human protein by using the enzyme reverse transcriptase to make a DNA copy of the mRNA for factor VIII, inserting this DNA into a plasmid with a marker gene, and introducing the plasmid into cultured hamster cells.
(a)
What is the DNA copy made from the mRNA called?
[1 mark]
AGenomic DNA
BRibosomal DNA
CPlasmid DNA
DComplementary DNA (cDNA)
(b)
Why can a human gene be expressed in hamster cells?
[1 mark]
AHamster cells contain the same genes as humans
BThe plasmid carries out the transcription and translation
CThe genetic code and the mechanisms of transcription and translation are universal
DHamster cells do not contain any DNA of their own
(c)
Explain the purpose of the marker gene.
[2 marks]
Total for question 2: 4 marks
3
A museum holds the bone of an extinct bird. DNA extracted from the bone contains about 40 copies of a target gene sequence. A technician amplifies this sequence using the polymerase chain reaction (PCR) for 30 cycles. Assume that the number of copies of the sequence doubles in every cycle.
(a)
Calculate the number of copies of the target sequence after 30 cycles.
[3 marks]
(b)
Describe what happens at each of the three temperature stages of one PCR cycle, and explain why a heat-stable DNA polymerase is used.
[4 marks]
Total for question 3: 7 marks
4
Warfarin is a drug that reduces blood clotting. The correct dose varies greatly between patients, because variant alleles of two genes affect how quickly the body breaks warfarin down. A test uses labelled DNA probes to identify these alleles in a patient's DNA. In a trial, 500 patients were given a dose chosen using the result of the genetic test and 500 patients were given the standard dose. In the first three months 20 of the patients given a dose chosen using the test had a major bleeding episode, compared with 45 of those given the standard dose. The test costs £60 per patient and the result takes two days. Some patients need warfarin at once because a clot has just been found. Some patients are worried about who may see their genetic information.
(a)
Describe how a labelled DNA probe can be used to find out which alleles of a gene a patient has, and explain how the result is used in personalised medicine.
[6 marks]
(b)
Evaluate whether all patients starting warfarin should be screened using the genetic test.
[6 marks]
Total for question 4: 12 marks
5
A trading standards laboratory is checking whether sacks labelled as an expensive variety of rice really contain that variety. The laboratory extracts DNA from grains, amplifies sections of DNA containing variable number tandem repeats (VNTRs) by PCR, and separates the fragments by gel electrophoresis to produce a genetic fingerprint.
(a)
What difference between individuals produces different genetic fingerprints?
[1 mark]
AThe number of chromosomes in each cell
BThe sequence of amino acids in a protein
CThe number of repeats of short base sequences at VNTR sites in non-coding DNA
DThe type of sugar in the DNA nucleotides
(b)
In gel electrophoresis, which DNA fragments travel the furthest?
[1 mark]
AThe shortest fragments
BThe longest fragments
CThe fragments with the most guanine
DThe fragments carrying a label
(c)
Explain why genetic fingerprinting can distinguish different varieties of rice, even though all rice plants have VNTRs.
[2 marks]
Total for question 5: 4 marks
6
Golden rice is a variety of rice that contains a gene from a maize plant and a gene from a bacterium, which together allow the grains to make beta-carotene. The body converts beta-carotene into vitamin A. It was developed to help prevent vitamin A deficiency in children in regions where rice is the main food. Parts of the technology used to make it are patented by large companies.
(a)
Why is golden rice described as transgenic?
[1 mark]
AIts genes were mutated by radiation
BIt contains genes transferred from other species
CIt was produced by crossing two varieties of rice
DIt has lost one of its genes
(b)
Which of the following is a humanitarian argument in favour of golden rice?
[1 mark]
APollen may transfer the genes to wild relatives
BCompanies may hold patents on part of the technology
CFarmers may become dependent on buying seed
DIt could reduce vitamin A deficiency in children who eat rice as a staple food
(c)
Give two reasons why environmentalists or anti-globalisation activists might oppose growing crops such as golden rice.
[2 marks]
Total for question 6: 4 marks
7
Scientists have sequenced the genome of a flowering plant. The genome has 120 million base pairs and about 27 000 protein-coding genes. The mean length of the coding sequence of a gene is 1500 base pairs.
(a)
Calculate the percentage of the genome that codes for proteins. Give your answer to two significant figures.
[3 marks]
(b)
Explain why the proteome of this plant cannot be predicted easily from its genome, and suggest how sequencing methods have improved over time.
[4 marks]
Total for question 7: 7 marks
8
A recessive condition causes inherited blindness because retinal cells lack a working copy of a gene. In gene therapy a healthy copy of the gene is inserted into a harmless virus, which is then injected into the retina. In a trial of 31 patients, 21 had improved vision in dim light after one year, and the effect lasted for at least three years. The treatment costs £250 000 per patient. Without treatment the condition leads to severe sight loss, and the lifetime care costs the health service more than this. The company that developed the treatment holds the patents and sets the price. The gene is inserted only into retinal cells.
(a)
Explain how recombinant DNA technology is used to make the virus carrying the healthy gene, and how it allows the retinal cells to make the missing protein.
[6 marks]
(b)
Evaluate the use of this gene therapy, using the information about the trial and its cost.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).