Question 2
2
Gold ions ( \(\mathrm{Au}^{3+}\) ) are toxic to most microorganisms. However, the bacterium Delftia acidovorans is frequently found in sticky layers, called biofilms, that form on the surface of gold deposits. D. acidovorans produces a peptide synthase that catalyses the synthesis of a small peptide called delftibactin. When isolated, delftibactin can precipitate \(\mathrm{Au}^{3+}\) ions as small particles of metallic gold. Delftibactin is a secondary metabolite.
structured0 marks
Question 2(d)
2(d)
The secondary metabolite, delftibactin, could be used to remove the toxic \(\mathrm{Au}^{3+}\) ions that are present in the waste produced by gold mining. Describe how delftibactin could be produced on a large scale.
Hardstructured5 marks
Answer
1 grow the wild-type, bacterium / D. acidovorans ; 2 in fermenter ; 3 ref. to (fed) batch culture ; 4 ref. to sterilised ; 5 nutrients at start (batch)/nutrients at intervals (fed) ; 6 carbon/nitrogen, sources ; 7 ref. to aeration / provide oxygen ; 8 ref. to constant temperature/water jacket; A environmental conditions kept constant 9 details of fermenter ; e.g. paddles / stirrers 10 harvest delftibactin / downstream processing ; [Total:15]
Question 2
2
The patty pan squash plant, Cucurbita pepo, produces edible fruits that vary in colour.
structured12 marks
Question 2(b)
2(b)
In 1994, two new varieties of squash were grown in the USA. Both varieties showed resistance to two viral diseases of squash plants. - The variety 'Tigress' was developed by selective breeding. - The variety 'Freedom II' was developed by adding genes for viral coat proteins to the squash genome.
structured4 marks
Question 2(b)(i)
2(b)(i)
Identify, with reasons, the variety of squash that can be described as recombinant.
Mediumstructured2 marks
Answer
Freedom II because: 1 contains, viral / foreign, DNA / genes or has DNA from 2 different, sources / organisms ; 2 ref. to genetic engineering / GMO / genetic modification / transgenic ;
Question 2(b)(ii)
2(b)(ii)
Outline one social advantage and one social disadvantage of the recombinant squash variety compared to non-resistant squash varieties. advantage disadvantage
Mediumstructured2 marks
Answer
advantage: improved yield / plants do not die of disease / crop not lost ; disadvantage: viral proteins might cause allergies / may be social resistance to GM crops ;
Question 2
2
0 marks
Question 2(c)
2(c)
One goal of genetic engineering is to make crops that are heat tolerant. This means that crops can grow and produce a good yield at high environmental temperatures. Use the information given in Question 2 to suggest and explain a way to improve the tolerance of a crop to high temperatures.
Hardstructured2 marks
Answer
any two from: 1 take, gene / (c)DNA, for rubisco activase ; 2 from, cotton and insert into, (false) flax / (named crop) plant / embryo ; 3 to maintain rubisco action at, high temperatures \(/>37.5^{\circ} \mathrm{C} /\) up to \(42.5^{\circ} \mathrm{C}\); 4 AVP ;
Question 2
2
The summer squash plant, Cucurbita pepo, produces edible fruits that vary in shape. Fig. 2.1 shows the fruits of three different varieties of squash plants. Fruit shape in squashes is controlled by two genes, A / a and B / b, that are located on different chromosomes. - A disc-shaped fruit is produced when both dominant alleles, A and B, are present. - A spherical fruit is produced when either allele A or allele B is present, but not if both A and B are present. - A long fruit is produced when both allele A and allele B are absent.
structured12 marks
Question 2(b)
2(b)
0 marks
Question 2(b)(i)
2(b)(i)
Genetically modified (GM) summer squash plants with resistance to viral diseases have been grown in the USA since 1995. Scientists have been concerned that viral resistance genes pass easily from GM squash plants to their wild relative, the Texas gourd, Cucurbita texana. Explain why the possibility of gene flow from GM squash plants to the Texas gourd is a cause of social and environmental concern. social environmental
Hardstructured2 marks
Answer
any two from: 1 gourds might become invasive ; 2 more competition from gourds might reduce food production ; 3 might harm gourd genetic diversity ; 4 resistant gourds might have, unknown / adverse, effects on ecosystem ;
Question 2(b)(ii)
2(b)(ii)
A study compared the survival of two different types of hybrids that were formed by cross-pollination between GM virus-resistant squash plants and wild Texas gourd plants: - virus-resistant hybrids that had inherited the viral resistance gene - non-resistant hybrids that had not inherited the viral resistance gene. Viral disease outbreaks caused many of the non-resistant hybrids to die. Leaf-eating beetles then moved in larger numbers to the surviving healthy virus-resistant hybrids. The beetles carried a pathogenic bacterium Erwinia which was capable of killing the plants. Fig. 2.2 compares infection with Erwinia in the virus-resistant hybrids and the non-resistant hybrids. Discuss whether these results provide support for the use of genetically modified organisms (GMOs) in food production.
Hardstructured2 marks
Answer
any two from: 1 resistance gene makes hybrids more susceptible to Erwinia ; 2 gene flow less of a problem than predicted (for this GMO) ; 3 GM squashes are 'safe' to grow ; 4 AVP ; e.g. could still be a problem in areas lacking, beetle / Erwinia
Question 2(b)(iii)
2(b)(iii)
Suggest why the GM virus-resistant squashes grown by farmers rarely suffer infection by Erwinia.
Mediumstructured1 marks
Answer
insecticides used to, kill beetle vector / prevent beetles spreading Erwinia or beetles may only feed on hybrids ;
Question 2
2
Domestic goats are small, herbivorous animals that provide milk for human use. This is an important source of food for people in rural South Africa. Three Northern European goat varieties (breeds) have been imported to South Africa because they have higher milk yields than the native South African goats. Table 2.1 compares the mean daily milk yields of these three breeds of Northern European goat in three locations, Northern Europe, Barbados and South Africa.
structured0 marks
Question 2(d)
2(d)
Children in developing countries may drink unpasteurised goats' milk. Some may develop diarrhoea caused by live bacteria ingested in the milk. Scientists have used genetic engineering to develop goats that produce human lysozyme in their milk. Lysozyme is an enzyme that kills bacteria and so reduces the number of bacteria in the milk. State a social advantage and a social disadvantage of making these GM goats available in developing countries. advantage disadvantage
Mediumstructured2 marks
Answer
any one advantage: 1 stops / reduces, diarrhoea (in children) ; 2 improves children's, nutrition / growth / development ; any one disadvantage: 3 safety risks unknown / potential allergen / side effects ; 4 may disrupt ('good') bacteria / AW ; 5 expensive ; 6 not willing to drink GM milk ;
Question 3
3
0 marks
Question 3(b)
3(b)
In 2012, permission was granted for a field trial in the UK of genetically modified T. aestivum. The wheat carries a gene, taken from peppermint plants, that results in the wheat leaves releasing a volatile, non-toxic chemical, (E)- \(\beta\)-farnesene (E \(\beta \mathrm{f}\) ), into the atmosphere. \(\mathrm{E} \beta \mathrm{f}\) is not only produced by various species of plants. It is also secreted by aphids when they are disturbed by a predator. Two experiments have been performed into the effect of \(\mathrm{E} \beta \mathrm{f}\) on the behaviour of aphids feeding on leaves in closed containers. Experiment 1 Either \(10 \mathrm{~cm}^{3}\) of air from a syringe that contained plant leaves that secrete \(\mathrm{E} \beta \mathrm{f}\) or \(\quad 10 \mathrm{~cm}^{3}\) of air from a syringe with no such leaves was added to the containers of feeding aphids. Experiment 2 Either \(20 \mathrm{~cm}^{3}\) of air containing 50 ng of \(\mathrm{E} \beta \mathrm{f}\) or \(20 \mathrm{~cm}^{3}\) of air containing no \(\mathrm{E} \beta \mathrm{f}\) was added to the containers of feeding aphids. In both experiments, the number of aphids that stopped feeding and moved away from the food leaves was counted. The results are shown in Table 3.1.
structured7 marks
Question 3(b)(ii)
3(b)(ii)
Other experiments show that \(\mathrm{E} \beta \mathrm{f}\) attracts predators of aphids, such as ladybirds. Explain how growing genetically modified wheat secreting \(\mathrm{E} \beta \mathrm{f}\) could increase the yield of wheat.
Mediumstructured3 marks
Answer
\(\mathrm{E} \beta \mathrm{f}\) stops aphids settling ; \(\mathrm{E} \beta \mathrm{f}\) attracts, predators of aphids/ladybirds ; attacked aphids secrete more \(\mathrm{E} \beta \mathrm{f}\); aphids not, eating/taking nutrients from, wheat;
Question 3(b)(iii)
3(b)(iii)
Suggest why growing this genetically modified wheat might be acceptable to people who object to the growth of genetically modified insect-resistant maize or cotton.
Mediumstructured0 marks
Answer
gene/E \(\beta\) f, already in, peppermint/various plant species ; \(\mathrm{E} \beta \mathrm{f}\) not, toxic/harmful to human health ; no new chemical added to human diet ; does not kill insects (unlike Bt maize or cotton) ; aphids still available for, predators/food web ;
Question 3
3
0 marks
Question 3(b)
3(b)
In 2012, permission was granted for a field trial in the UK of genetically modified T. aestivum. The wheat carries a gene, taken from peppermint plants, that results in the wheat leaves releasing a volatile, non-toxic chemical, (E)- \(\beta\)-farnesene (E \(\beta \mathrm{f}\) ), into the atmosphere. \(\mathrm{E} \beta \mathrm{f}\) is not only produced by various species of plants. It is also secreted by aphids when they are disturbed by a predator. Two experiments have been performed into the effect of \(\mathrm{E} \beta \mathrm{f}\) on the behaviour of aphids feeding on leaves in closed containers. Experiment 1 Either \(10 \mathrm{~cm}^{3}\) of air from a syringe that contained plant leaves that secrete \(\mathrm{E} \beta \mathrm{f}\) or \(\quad 10 \mathrm{~cm}^{3}\) of air from a syringe with no such leaves was added to the containers of feeding aphids. Experiment 2 Either \(20 \mathrm{~cm}^{3}\) of air containing 50 ng of \(\mathrm{E} \beta \mathrm{f}\) or \(20 \mathrm{~cm}^{3}\) of air containing no \(\mathrm{E} \beta \mathrm{f}\) was added to the containers of feeding aphids. In both experiments, the number of aphids that stopped feeding and moved away from the food leaves was counted. The results are shown in Table 3.1.
structured7 marks
Question 3(b)(ii)
3(b)(ii)
Other experiments show that \(\mathrm{E} \beta \mathrm{f}\) attracts predators of aphids, such as ladybirds. Explain how growing genetically modified wheat secreting \(\mathrm{E} \beta \mathrm{f}\) could increase the yield of wheat.
Mediumstructured3 marks
Answer
\(\mathrm{E} \beta \mathrm{f}\) stops aphids settling ; \(\mathrm{E} \beta \mathrm{f}\) attracts, predators of aphids/ladybirds ; attacked aphids secrete more \(\mathrm{E} \beta \mathrm{f}\); aphids not, eating/taking nutrients from, wheat;
Question 3(b)(iii)
3(b)(iii)
Suggest why growing this genetically modified wheat might be acceptable to people who object to the growth of genetically modified insect-resistant maize or cotton.
Mediumstructured0 marks
Answer
gene/E \(\beta\) f, already in, peppermint/various plant species ; \(\mathrm{E} \beta \mathrm{f}\) not, toxic/harmful to human health ; no new chemical added to human diet ; does not kill insects (unlike Bt maize or cotton) ; aphids still available for, predators/food web ;
Question 3
3
Oil seed rape (canola), Brassica napus, has been genetically modified to be resistant to herbicides containing glufosinate ammonium. The genetically modified (GM) oil seed rape contains the bar gene, obtained from a soil bacterium. This gene codes for an enzyme that converts glufosinate ammonium into a non-toxic compound.
structured0 marks
Question 3(a)
3(a)
Outline the advantages to farmers of growing glufosinate-resistant oil seed rape.
Mediumstructured2 marks
Answer
\(\max 2\) of: 1 can, kill / control, weeds ; R kill, insects / pests 2 reduce competition / increase yield (of rape) ; 3 AVP ; e.g. manual weeding / hoeing, difficult / expensive ref. to glufosinate converted to non-toxic compound
Question 3(c)
3(c)
The pollen of oil seed rape is transferred from one flower to another by insects. After pollination, fertilisation and seed formation can occur. One of the potential problems of growing glufosinate-resistant oil seed rape is that pollen from these plants could be transferred to the flowers of wild relatives, such as wild radish, Raphanus raphanistrum. This could result in genetic changes in these wild species. An experiment was carried out to investigate whether glufosinate-resistant hybrids between GM oil seed rape and wild radish plants are likely to compete successfully with non-hybrid or non-resistant plants in the natural environment. - Type 1 hybrids were produced by transferring pollen from wild radish (diploid number 18) to glufosinate-resistant oil seed rape (diploid number 38). - Type 2 hybrids were produced by transferring pollen from glufosinate-resistant oil seed rape to wild radish. - Each hybrid was then crossed with wild radish over several generations. - The resulting offspring were then grown in field trials, together with normal wild radish. - The height of the plants and number of seeds each produced were measured. Then the plants were tested for the bar gene. Table 3.1 shows the results.
structured0 marks
Question 3(c)(iii)
3(c)(iii)
Many varieties of GM oil seed rape are male sterile, meaning that they do not produce pollen. With reference to Table 3.1, suggest the advantages to the environment of growing male sterile varieties of GM oil seed rape, rather than GM varieties that produce pollen.
Hardstructured3 marks
Answer
max 3 of: advantage of male sterile GM variety 1 avoid transferring, bar/resistance, gene to wild, radish/relations; ora 2 avoid superweeds ; ora 3 avoid type 2 hybrids ; ora disadvantage of type 2 hybrids (from GM variety that produces pollen) 4 taller (than wild radish) ; A very tall / \(88 \mathrm{~cm} / 95 \mathrm{~cm}\) 5 produce, more / many, seeds (than wild radish) ; A 3958 / 443 more 6 may (out)compete, wild radish / crops ;
Question 4
4
0 marks
Question 4(b)
4(b)
Give two advantages of genetically engineering herbicide resistance in crop plants such as soybean.
Easystructured2 marks
Answer
any two from: 1 high / increase in, yield / productivity / quality or more food ; 2 increased income / reduce costs ; 3 can use herbicides / AW ; 4 less / no, competition ; 5 no need to plough / less labour intensive ;
Question 3
3
Salmon can be genetically modified (GM) to produce increased quantities of growth hormone, which is a protein. GM salmon modified in this way have a faster growth rate and reach their maximum body mass at a younger age than non-GM salmon.
structured10 marks
Question 3(b)
3(b)
Scientists investigated whether injection of very young non-GM salmon with recombinant growth hormone could cause an increase in the growth rate of the salmon. The scientists used two groups of non-GM salmon: - a control group of salmon that were not injected with recombinant growth hormone - an experimental group of salmon that were injected with \(1.0 \mu \mathrm{~g}\) of recombinant growth hormone at the start of the experiment and once a week for the next six weeks. The mean body mass of the salmon in the two groups at the start of the experiment was the same ( 5.3 g ). After six weeks, the body mass of every salmon was measured again. The results are summarised in Table 3.1. A student decided that a t-test should be performed on the results shown in Table 3.1.
structured7 marks
Question 3(b)(iii)
3(b)(iii)
Suggest one advantage, other than cost, of farming GM salmon that produce increased quantities of growth hormone instead of farming non-GM salmon that are injected with recombinant growth hormone each week.
Mediumstructured1 marks
Answer
any one from: 1 idea of less labour intensive ; e.g. no need for weekly injections / GM only needs to be done once 2 idea of less stressful on GM salmon ; 3 risk of infection with injections ; 4 idea that growth hormone is continuously produced ; 5 GM salmon may grow faster ;