19.3. Genetically modified organisms in agriculture
A subsection of Biology, 9700, through 19. Genetic technology
Listing 10 of 27 questions
shows the area of land that was used to grow genetically modified (GM) crops in the USA, Brazil, India and China from 2004 to 2015. year area of land used to grow GM crops / million hectares 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 USA Brazil India China key Suggest reasons why the area of land used to grow GM crops in the USA is greater than the area of land used to grow GM crops in Brazil. Describe the differences in the area of land that was used to grow GM crops in China and the area of land that was used to grow GM crops in India, over the time shown in . Genetic modifications in crops can provide resistance to insect pests. Bt maize is one type of GM crop that has been produced to be resistant to insect pests. State two benefits to farmers of insect resistance in crops. Describe the difference between Bt maize and non-GM maize that explains why Bt maize is resistant to insects. State two reasons why people may have objections to the growth of insect-resistant GM crops. In 2015, the percentage of the USA population that objected to the use of GM crops was lower than in 2005. Suggest why a smaller percentage of the USA population objected to the use of GM crops in 2015.
9700_m19_qp_42
THEORY
2019
Paper 4, Variant 2
View
Vitamin A deficiency is a widespread public health problem. One source of vitamin A is carotene in the diet. Carotene can be converted to vitamin A in the body. White rice grains are not a dietary source of vitamin A because they do not contain carotene. Scientists have genetically modified a variety of rice to improve the diet of people who are vitamin A deficient. The grains of this genetically modified rice contain carotene. Describe how genetic engineering could be used to modify a variety of rice so that the grains contain carotene. In a 2018 report, the United Nations Children’s Fund (UNICEF) estimated that: • more than 140 million children are at high risk of vitamin A deficiency • 1.15 million child deaths are caused by vitamin A deficiency each year. Vitamin A deficiency is also a leading cause of childhood blindness. The recommended dietary allowance (RDA) of vitamin A for a 5-year-old child is 400 μg per day. Genetically modified (GM) rice contains 12 μg of carotene per gram of rice. In 2018, four countries approved GM rice as safe to eat. The development of GM rice has been partly paid for by governments. It has been agreed that seeds of GM rice will be made available to farmers in countries with high levels of poverty at the same cost as seeds of normal rice. Some international organisations, such as Greenpeace, campaign against all GM crops. More than 100 respected scientists have asked Greenpeace to stop campaigning against GM rice. Discuss social and ethical arguments that support the position of the scientists.
9700_m21_qp_42
THEORY
2021
Paper 4, Variant 2
View
In the USA, about 35% of all maize that is grown has been genetically modified to produce a toxin, called Bt toxin, derived from the bacterium Bacillus thuringiensis. The genetically modified plants are known as Bt maize. Explain the advantages of growing Bt maize. An investigation was carried out into the potential effects of dead leaves from Bt maize on organisms living in streams that flow through areas where the maize is grown. The researchers conducted a laboratory-based experiment in which larvae of one species of aquatic caddis fly, Lepidostoma liba, were fed on non-Bt maize leaves, or on leaves from Bt maize. The growth rates of the larvae were measured. The results are summarised in . 0.0 0.5 1.0 non-Bt maize Bt maize mean growth rate / arbitrary units Describe the effect of eating leaves from Bt maize on the growth rate of L. liba larvae. In a second laboratory-based experiment, three groups of larvae of a different species of caddis fly, Helicopsyche borealis, were fed on pollen containing: A no Bt toxin B Bt toxin at concentrations found in streams in maize-growing areas C Bt toxin at concentrations twice as high as found in those streams. The researchers measured the mortality rates of the caddis fly larvae. Their results are summarised in Table 5.1. Table 5.1 groups compared difference in mortality rate groups A and B no significant difference groups A and C significantly greater mortality in C than in A The researchers were careful to state that their results showed the ‘potential ecological effects’ on the caddis fly larvae of growing Bt maize. Suggest two reasons why ‘potential ecological effects’ is a suitable description of any conclusions that could be drawn from the results of this experiment. When the results of the experiments described in and were published, many other scientists criticised the research very strongly. Suggest why some scientists might wish to suppress results such as these, even if there is no fault with the investigation itself.
9700_s11_qp_42
THEORY
2011
Paper 4, Variant 2
View
In the USA, about 35% of all maize that is grown has been genetically modified to produce a toxin, called Bt toxin, derived from the bacterium Bacillus thuringiensis. The genetically modified plants are known as Bt maize. Explain the advantages of growing Bt maize. An investigation was carried out into the potential effects of dead leaves from Bt maize on organisms living in streams that flow through areas where the maize is grown. The researchers conducted a laboratory-based experiment in which larvae of one species of aquatic caddis fly, Lepidostoma liba, were fed on non-Bt maize leaves, or on leaves from Bt maize. The growth rates of the larvae were measured. The results are summarised in . 0.0 0.5 1.0 non-Bt maize Bt maize mean growth rate / arbitrary units Describe the effect of eating leaves from Bt maize on the growth rate of L. liba larvae. In a second laboratory-based experiment, three groups of larvae of a different species of caddis fly, Helicopsyche borealis, were fed on pollen containing: A no Bt toxin B Bt toxin at concentrations found in streams in maize-growing areas C Bt toxin at concentrations twice as high as found in those streams. The researchers measured the mortality rates of the caddis fly larvae. Their results are summarised in Table 5.1. Table 5.1 groups compared difference in mortality rate groups A and B no significant difference groups A and C significantly greater mortality in C than in A The researchers were careful to state that their results showed the ‘potential ecological effects’ on the caddis fly larvae of growing Bt maize. Suggest two reasons why ‘potential ecological effects’ is a suitable description of any conclusions that could be drawn from the results of this experiment. When the results of the experiments described in and were published, many other scientists criticised the research very strongly. Suggest why some scientists might wish to suppress results such as these, even if there is no fault with the investigation itself.
9700_s11_qp_43
THEORY
2011
Paper 4, Variant 3
View
Food crops like wheat may be improved by selective breeding and genetic modification. Outline how wheat crops have been improved by selective breeding. Variation in height of a strain of wheat plants in a field shows a continuous pattern of variation. Explain what is meant by continuous variation and explain why this type of variation occurs in a population. Wheat and other crops have been genetically modified to be resistant to the herbicide glyphosate since 1996. shows the area of glyphosate-resistant crops grown as a percentage of the total planted hectares (plotted points) and the number of weed species with resistance to glyphosate . percentage of planted hectares number of resistant weed species year area resistant species Describe and explain the relationship between the area of glyphosate-resistant crops grown and the number of resistant weed species. Suggest one social advantage and one environmental advantage of growing glyphosate-resistant wheat. social advantage environmental advantage
9700_s16_qp_42
THEORY
2016
Paper 4, Variant 2
View
Oil seed rape , 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. Outline the advantages to farmers of growing glufosinate-resistant oil seed rape. The bar gene was introduced into the oil seed rape using plasmids. The plasmids also contained a promoter taken from thale cress, Arabidopsis thaliana. Outline the structure of a plasmid. Explain how the properties of plasmids make them suitable for use during genetic modification programmes. Describe the role of a promoter in gene expression. 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. Table 3.1 type of plant number of seeds per plant mean height / cm presence of bar gene offspring from type 1 hybrid and wild radish 22.3 absent 28.3 present offspring from type 2 hybrid and wild radish 88.7 absent 95.0 present wild radishes 76.5 absent Predict the diploid number of chromosomes in a hybrid between oil seed rape and wild radish. Suggest how the researchers could have determined whether or not the bar gene was present in the plants. 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.
9700_s17_qp_41
THEORY
2017
Paper 4, Variant 1
View
Weeds reduce crop yields by competing with crop plants for space, light, water and minerals. The modes of action of three different types of herbicide are summarised in Table 4.1. Table 4.1 type of herbicide mode of action year of first widespread use photosystem II inhibitor prevents photophosphorylation ALS inhibitor prevents synthesis of the amino acids isoleucine, leucine and valine glyphosate prevents synthesis of the amino acids phenylalanine, tryptophan and tyrosine shows the cumulative number of species of weeds that have become resistant to these three types of herbicide since 1960. number of species year ALS inhibitor ALS inhibitor photosystem II inhibitor photosystem II inhibitor glyphosate glyphosate Describe how the number of weed species resistant to herbicides has changed since 1960. Explain how a weed species becomes resistant to a herbicide. ALS inhibitor herbicides work by binding to an enzyme present in chloroplasts called acetolactate synthetase (ALS). ALS is a globular protein consisting of four identical polypeptides each composed of 668 amino acids. The primary structure of the ALS polypeptide of each weed species resistant to ALS inhibitor herbicides has been sequenced. Amino acid substitutions at positions as far apart as position 122 and position 574 can result in resistance. The gene that codes for the ALS polypeptide does not contain any non-coding sections . The first amino acid in the final polypeptide is methionine. State the number of base pairs in the gene that codes for an ALS polypeptide. Explain why resistance to ALS inhibitor herbicide can result from substitutions of amino acids that are far apart in the primary sequence. Genetic modification is one method used to develop herbicide resistance in crop plants. Other methods include: method 1: crossing a crop plant with a herbicide-resistant wild plant belonging to the same genus and then applying the herbicide method 2: causing mutations in the crop plants and then applying the herbicide. State two benefits of using method 1 and two benefits of using method 2 to develop herbicide resistance in crop plants. method 1 method 2
9700_s17_qp_42
THEORY
2017
Paper 4, Variant 2
View
Oil seed rape , 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. Outline the advantages to farmers of growing glufosinate-resistant oil seed rape. The bar gene was introduced into the oil seed rape using plasmids. The plasmids also contained a promoter taken from thale cress, Arabidopsis thaliana. Outline the structure of a plasmid. Explain how the properties of plasmids make them suitable for use during genetic modification programmes. Describe the role of a promoter in gene expression. 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. Table 3.1 type of plant number of seeds per plant mean height / cm presence of bar gene offspring from type 1 hybrid and wild radish 22.3 absent 28.3 present offspring from type 2 hybrid and wild radish 88.7 absent 95.0 present wild radishes 76.5 absent Predict the diploid number of chromosomes in a hybrid between oil seed rape and wild radish. Suggest how the researchers could have determined whether or not the bar gene was present in the plants. 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.
9700_s17_qp_43
THEORY
2017
Paper 4, Variant 3
View
Maize, Zea mays, is an important food crop for human consumption and for feeding to animals. Two varieties of maize are MON810 and Justina. Justina has been developed in the traditional way by selective breeding (artificial selection) and MON810 is an example of a genetically modified (GM) organism. MON810 produces a chemical that is toxic to insect pests. It is described as insect-resistant. Outline how genetic engineering gave MON810 the trait of insect resistance. Countries vary in the extent to which they grow GM varieties such as MON810, instead of traditional varieties such as Justina. • In the USA, 88% of the total maize that is grown is GM. • In most European countries, 0% of the maize that is grown is GM. Scientists used computer models to predict the effect of two different changes in agricultural practice on maize crop yields: • a global ban that reduces the cultivation of GM maize to 0% everywhere • all countries increasing the cultivation of GM maize to the 88% level of the USA. Table 6.1 shows the results of this modelling for four countries. Table 6.1 country percentage change in yield of maize decrease GM maize cultivation to 0% of total increase GM maize cultivation to 88% of total Argentina –8.86 +2.90 Honduras –1.26 +16.75 Spain –3.82 +5.39 USA –7.63 0.00 Explain what the data in Table 6.1 suggests about the social and ethical implications of growing GM maize.
9700_s19_qp_41
THEORY
2019
Paper 4, Variant 1
View
Questions Discovered
27