19.1. Principles of genetic technology
A subsection of Biology, 9700, through 19. Genetic technology
Listing 10 of 43 questions
Interferon-alpha (IFN-α) can be produced as a recombinant human protein to treat some types of cancer. The gene IFNA2 codes for IFN-α. One method of producing recombinant IFN-α uses genetically engineered Escherichia coli bacteria that contain recombinant plasmids. Each recombinant plasmid contains: • the gene IFNA2 • three regulatory sequences of the lac operon (promoter, operator and lac• a gene for antibiotic resistance, AMPR. Each of the sequences for the lacI gene and AMPR gene contains its own promoter. As a result, these genes are always expressed in E. coli bacteria that contain this recombinant plasmid. is a diagram of the recombinant plasmid. The promoter regions of the lacI gene and AMPR gene are not shown. IFNA2 AMPR lacI o p e r a t o r p r o m o t e r The start of transcription of the gene IFNA2 by E. coli with the recombinant plasmid shown in needs to be controlled to obtain an optimum yield of IFN-α. Scientists investigated the effect of two inducers of transcription on the production of recombinant IFN-α: • lactose, which is converted to allolactose in E. coli • IPTG, which is a synthetic molecule with a very similar structure to allolactose. IPTG cannot be broken down by E. coli. The scientists grew three cultures of E. coli containing the recombinant plasmid in the same growth medium. The growth medium contained glucose, amino acids, essential vitamins and minerals. The growth medium did not contain lactose. After four hours, either lactose or IPTG at the same concentration was added to two of the cultures of E. coli. As a control, the third culture of E. coli was grown without adding lactose or IPTG. The concentration of recombinant IFN-α in the cultures was measured at different times over a period of 28 hours. The results are shown in . time / hours concentration of IFN-α / μg dm–3 key culture to which IPTG added culture to which lactose added control culture The regulatory sequences of the lac operon contained in the recombinant plasmid are involved in the control of transcription of the gene IFNA2. Explain the role of the gene lacI in the control of transcription of the IFNA2 gene between 0 hours and 4 hours. With reference to , describe the changes in the concentration of recombinant IFN-α in the culture containing IPTG from when IPTG was added at 4 hours to the end of the experiment at 28 hours. Suggest one reason for the difference between the concentration of recombinant IFN-α in the culture at 8 hours in the presence of lactose and the concentration of recombinant IFN-α in the culture at 8 hours in the presence of IPTG. Suggest one reason for the change in the concentration of recombinant IFN-α in the culture containing IPTG from 12 hours to 16 hours. The gene AMPR in the plasmid shown in codes for a protein that provides resistance to the antibiotic ampicillin. Suggest how AMPR allows genetically engineered E. coli containing the recombinant plasmid to be identified. Bacteria can evolve antibiotic resistance through natural processes. Outline how bacteria can evolve to become resistant to antibiotics.
9700_m23_qp_42
THEORY
2023
Paper 4, Variant 2
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Scientists grew bacteria in a medium containing heavy nitrogen, 15N, as the only source of nitrogen. After many generations, all of the bacterial DNA contained heavy nitrogen. These bacteria were then moved from the heavy nitrogen medium into a medium with only light nitrogen, 14N. Some bacteria were collected from each of the next three generations and their DNA was analysed. Hybrid DNA contains both heavy and light nitrogen. Which row shows the correct DNA of the first and third generations?
9700_s20_qp_11
MCQ
2020
Paper 1, Variant 1
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Gene technology has many uses including the production of substances such as insulin. Outline what is meant by gene technology. Explain why genes for enzymes that produce fluorescent substances are used as makers in gene technology. There is much controversy throughout the world regarding the use of genetically modified (GM) crops. Suggest two advantages of growing GM rice with an enhanced vitamin A content. Suggest two disadvantages of growing GM crops.
9700_s10_qp_42
THEORY
2010
Paper 4, Variant 2
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Gene technology has many uses including the production of substances such as insulin. Outline what is meant by gene technology. Explain why genes for enzymes that produce fluorescent substances are used as makers in gene technology. There is much controversy throughout the world regarding the use of genetically modified (GM) crops. Suggest two advantages of growing GM rice with an enhanced vitamin A content. Suggest two disadvantages of growing GM crops.
9700_s10_qp_43
THEORY
2010
Paper 4, Variant 3
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Pigs are farm animals used for livestock in some parts of the world. The first genetically modified pigs were produced in 1985. Foreign DNA was injected directly into the nuclei of zygotes. The foreign DNA was made up of two components: • the gene coding for human growth hormone • a section of mouse DNA that, in the presence of metal ions, allows transcription to begin. The human growth hormone synthesised by the transgenic pigs had the effect of making the pigs grow faster, larger and heavier than non-genetically modified pigs. Suggest reasons for this difference. Suggest and explain why the mouse DNA was included in the foreign DNA. Only 1% of the attempts successfully produced transgenic pigs. These pigs showed higher body mass and a greater muscle to fat ratio than normal pigs. Monitoring of the pigs’ behaviour revealed that they rested more than normal pigs, suffered from stomach ulcers and were unwilling to mate. Discuss whether these transgenic pigs have long term economic value. Comment on the ethics of producing transgenic pigs showing the features described. In 2015 pigs were produced that had part of their genome altered by a new technique. The technique involved: • an RNA sequence designed to bind to a specific targeted pig gene • a gene-editing enzyme that is able to cut out sections of DNA. The technique was used on pig zygotes that had been created by IVF. All the zygotes treated grew into piglets and these all showed large deletions in the targeted gene. This gene coded for a specific cell surface membrane protein. The piglets did not express the protein and this gave them resistance to infection by a virus that causes a serious disease in pigs. Describe two advantages of the gene-editing technique compared to the traditional genetic modification technique used to make transgenic pigs in 1985. A scientist stated that this new technique is a form of selective breeding, so is not genetic engineering. Discuss whether this statement is true and whether public groups who oppose transgenic animals will be more or less likely to accept the new technique.
9700_s18_qp_41
THEORY
2018
Paper 4, Variant 1
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In 1973 a technique for genetic engineering was used for the first time. Recombinant DNA was made using a plasmid and this was successfully transferred into an organism. In 2012 a new technique for genetic engineering, called gene editing, was developed. Table 4.1 lists some statements about the two genetic engineering techniques. Complete Table 4.1 to compare the original genetic engineering technique using a plasmid vector with the newer technique of gene editing. For each row, place a tick (3) in the correct column if the statement applies and leave a blank if the statement does not apply. Table 4.1 statement genetic engineering using a plasmid gene editing It can produce a transgenic organism. It can modify the characteristics of an organism. It can delete unwanted DNA. It uses an enzyme that cuts DNA. It can use RNA to precisely locate the target gene. Orange trees, Citrus sinensis, produce fruits that are an important food crop. The functional leaf area of orange trees may be reduced by the growth of citrus canker bacteria. These bacteria cause citrus canker disease. Scientists used gene editing to develop two types of orange tree with different mutations (changes to the DNA). The mutant orange tree leaves showed resistance to citrus canker disease. shows the area of leaf with citrus canker disease in wild type (not gene edited) and gene edited orange tree leaves after they have been exposed to citrus canker bacteria. 0.0 1.0 2.0 area of leaf with canker disease / mm2 3.0 0.5 1.5 2.5 3.5 A B C type of orange tree Identify the letter that represents the wild type orange trees on . Explain the social benefits of this example of gene editing.
9700_s22_qp_41
THEORY
2022
Paper 4, Variant 1
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In 1973, a technique for genetic engineering was used for the first time. Recombinant DNA was made using a plasmid and this was successfully transferred into an organism. In 2012, a new technique for genetic engineering, called gene editing, was developed. Table 4.1 lists some statements about the two genetic engineering techniques. Complete Table 4.1 to compare the original genetic engineering technique using a plasmid vector with the newer technique of gene editing. For each row, place a tick (3) in the correct column if the statement applies and leave a blank if the statement does not apply. Table 4.1 statement genetic engineering using a plasmid gene editing It may cause the organism to produce a different protein. It may cause a single base pair in a gene to be changed. The success of the technique can be evaluated using marker genes. It may use the CRISPR system. It uses DNA ligase. Cassava plants, Manihot esculenta, produce roots that have a high starch content. These roots are an important food source in tropical regions. The growth of cassava plants is reduced by competition from weeds. Scientists used gene editing to develop two types of cassava plant with different mutations (changes to the DNA). The gene edited cassava plants showed resistance to the herbicide glyphosate. In susceptible plants, glyphosate prevents synthesis of three amino acids from a precursor molecule called shikimate. shows the concentration of shikimate in the wild type (not gene edited) and the two types of gene edited cassava plant after they were exposed to three different concentrations of glyphosate. shikimate concentration / arbitrary units type of cassava plant Key: glyphosate / μmol dm–3 A B C Identify the letter in that represents the wild type cassava plant. Explain the social benefit of this example of gene editing.
9700_s22_qp_42
THEORY
2022
Paper 4, Variant 2
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In 1973, a technique for genetic engineering was used for the first time. Recombinant DNA was made using a plasmid and this was successfully transferred into an organism. In 2012, a new technique for genetic engineering, called gene editing, was developed. Table 4.1 lists some statements about the two genetic engineering techniques. Complete Table 4.1 to compare the original genetic engineering technique using a plasmid vector with the newer technique of gene editing. For each row, place a tick (3) in the correct column if the statement applies and leave a blank if the statement does not apply. Table 4.1 statement genetic engineering using a plasmid gene editing It can add a new phenotypic characteristic to an organism. It can change an A–T base pair to C–G. It can inactivate a desired selected gene in an organism. It may change DNA in a way that cannot be distinguished from a natural mutation. It requires a DNA donor and a recipient. Camelina sativa is a fast-growing plant with oil-rich seeds. C. sativa grows in dry and poor soils and so it may be important as a food crop in the future. The oil from its seeds has a high content of polyunsaturated fatty acids. This shortens the time that the oil can be stored for, which is a disadvantage. Scientists used gene editing to develop two types of C. sativa with different genetic changes. The gene edited C. sativa seeds produced oil with longer storage times. shows the percentage composition of fatty acids in the oil extracted from seeds of gene edited and wild type (not gene edited) C. sativa. 16:0 18:0 18:1 18:2 fatty acids shown as number of carbons:number of C=C double bonds percentage composition of fatty acids 18:3 20:1 22:1 type A type B type C Key Identify the letter that represents the oil of the wild type C. sativa on . With reference to , discuss the social benefits of this example of gene editing.
9700_s22_qp_43
THEORY
2022
Paper 4, Variant 3
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Green fluorescent protein (GFP) is a small protein that emits bright green fluorescence in blue light. It was first isolated from the jellyfish, Aequorea victoria. The gene coding for GFP can be expressed in bacteria, such as Escherichia coli, and so it is often used as a marker to show successful uptake of a gene by the bacterium. Outline how a gene from another species can be inserted into E. coli. Explain how a marker gene, such as the gene for GFP, is used to show successful uptake of a gene for a wanted protein. Genes for enzymes that produce fluorescent substances are often used as markers in gene technology. GFP is not an enzyme. Suggest one disadvantage of using the gene for GFP to produce easily detectable fluorescence, rather than using a gene for an enzyme that produces a fluorescent substance. Explain your answer. disadvantage explanation
9700_w12_qp_41
THEORY
2012
Paper 4, Variant 1
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Questions Discovered
43