Introduction Genetically modified (GM) foods are increasingly controversial as they become more widespread. They have met a barrage of criticism and protest, and public confidence in them is low. New legislation on labelling has been introduced, partly in response to the controversy. The companies with a stake in developing genetic modification have made substantial efforts to promote its claimed benefits, such as greater agricultural efficiency and cheaper, more nutritious, novel foodstuffs. Opponents of the technology press for a ban, claiming that genetic modifications endangers the environment, presents risks to human health, and threatens small and organic farmers by increasing the influence of large agricultural corporations. Modifying the genetic composition of crop plants or farm animals by selective breeding has been an important part of agriculture for thousands of years. However, the modern technology of genetic engineering has massively increased the scope for changing the characteristics of crops and livestock. This direct modification of an organism's genetic material (genome) bypasses conventional breeding methods, producing totally novel gene combinations that could never occur in nature. Artificial transfer between completely unrelated organisms is possible, because the genetic material in all organisms is built from DNA.
How does it work? Genetic modification usually involves identifying the genes governing a desirable characteristic in one organism, and inserting them into another in the expectation that the trait will be transferred. For example, a gene from certain bacteria, which causes them to produce the toxin Bt, has been inserted into a wide variety of crop plants, including cotton, apples, and maize. The transgenic (genetically transformed) plants produce Bt in their tissues, and are therefore less attractive to insect pests. Once the section of DNA containing the relevant gene has been identified, it is cut from the genome of the donor organism using specific enzymes, creating free fragments of the desired DNA. The standard method for inserting these fragments into another genome, first achieved in 1973, involves using DNA from a third organism as a vector. A vector is an agent that can be made to bind to a DNA fragment and transport it into another cell, where the fragment (but not the vector itself) is inserted into the host's DNA. A bacterial plasmid (a circle of DNA independent of the main bacterial chromosome) or a virus can be harnessed as a vector, because either may integrate into a foreign genome during its normal infective process. Therefore, the genetic engineer splices the DNA representing the desired gene into the chosen vector, and allows the modified plasmid or virus to integrate into the host genome, taking the extra gene with it. The vector is usually ‘tagged’ with a marker gene, for example one conferring antibiotic resistance, so that successfully transformed cells can be identified. There are several mechanical techniques for inserting DNA into cells. The most spectacular involves the use of DNA ‘bullets’. Microscopic metal beads can be coated with DNA fragments and propelled on a plastic pellet fired by a miniature gun into the host cell, where the DNA integrates into the genome. Genes have been introduced into the cells of various types of plant by this method.
Cheaper production and greater yield… The dramatic, rapid changes made possible by genetic engineering have a vast range of potential applications in the development of new marketable foodstuffs. GM crops may offer greater yields, pest and disease resistance, and tolerance to temperature extremes, drought, or salinity. Plants engineered to be resistant to general herbicides should be easier and cheaper to farm, as a whole field can be sprayed with a single herbicide, killing all plants except the resistant crop. Agricultural developments such as these aim for greater efficiency of production, which may be increasingly important as food supplies come under greater pressure from global population growth. To the consumer, GM foods may offer enhanced nutritional qualities, such as a lower fat content or increased levels of vitamins. Improved flavour, appearance, and longer shelf life are other objectives. There is also the prospect of plants engineered to contain specific ingredients of medical benefit, such as vaccines.
… but at what cost? However, some scientists have expressed concern about the risks associated with transgenic foodstuffs. Their studies have been used by protesters to support assertions that genetic modification is an unpredictable threat to the environment and to food safety. There is good evidence that transgenic crops can cross-pollinate with their wild relatives, introducing novel genetic combinations into the wider environment. This may have unknown ecological effects; for instance, some suggest that it could lead to the creation of ‘superweeds’ (weed plants that have acquired traits such as herbicide resistance from GM crops). It could also disrupt the life cycles of insects. For example, a 1999 study found that pollen from GM maize slowed the growth of caterpillars of the monarch butterfly compared with caterpillars that fed only on non-GM pollen. The introduction of GM organisms into the human food chain may also have unpredictable health effects. For example, there are fears that the widespread use of antibiotic-resistant vectors may allow the development of new lines of bacterial pathogens with antibiotic resistance. There are also concerns that novel DNA in foods may cause unforeseen allergic reactions in some people. Risks such as these illustrate that genetic engineering is often not as precise a technology as may be assumed. Although the ability to isolate and transfer specific genes is an impressive feat, it is not possible to predict exactly every effect of inserting a gene, nor its long-term stability in the genome. The actual extent of such potential problems should become clearer with time, and after more research.
On the shelves, behind the scenes Since their commercial introduction in 1996, several GM foodstuffs have come onto the market, ranging from tomato paste to salmon. Not all are sold in all countries; the USA currently has the largest number on sale. The most important modified foods are soya and maize. About 30% (21 million tonnes) of the 1998 US soya harvest came from modified plants, as did some 20% (40 million tonnes) of the total US maize crop. These GM crops are usually mixed with normal crops after harvest for use as ingredients in a wide range of processed foods. Additionally, GM foods can be found as agents in the food production process, rather than as foodstuffs in their own right. Examples include GM chymosin, used to make vegetarian cheese, and artificial bovine somatotropin (BST), a version of a cattle hormone synthesized by GM bacteria, which can be injected into cows to boost milk yields. Most processed foods may now either contain GM ingredients or use transgenic enzymes during production. All GM foods undergo legal scrutiny and testing before approval; assessment is based mainly on a comparison of a GM food with its conventional counterpart.
Regulation and testing There are a great many more GM foodstuffs under development. Research is subject to various legislation, particularly concerning the release of modified organisms into the environment or food chain. For example, only government-licensed trial plots of GM crops are currently permitted in the UK. However, the size and number of trials has increased as more crops are tested on farm-scale plots, each typically covering 10 hectares/25 acres. The Royal Society, which in 1998 concluded that GM plants offered potential benefits, retrenched in 2002, saying that more work was required on health and environmental issues. UK law requires that GM soya or maize be labelled in food shops and restaurants. Additionally, European Union regulations made in October 1999 extend the labelling requirements to the suppliers of restaurants and caterers, and permit accidental GM content in non-GM food up to a threshold level of 1%. In 2003, a Cabinet Office report stated that there was no financial or consumer benefit in growing GM crops in the UK ‘at present’.
Public fears and corporate control There is still a general uncertainty about GM's potential impacts. Some people hold ethical objections to the very idea of manipulating the basis of inheritance or the patenting of living organisms, especially where animals are involved. Public concern about possible health risks has made genetic modification an important public health issue in Europe and North America, with opinion polls indicating a majority opposed to GM food. Resistance to transgenic plants increased in Britain in 1998 and 1999, leading to activists destroying crops at many separate sites. A series of high-profile direct actions against farm-scale trials began in the summer of 1999, with numerous arrests. Many local groups were formed to campaign against genetic engineering within food and agriculture. There are also fears about the power of large biotechnology corporations to control agricultural markets. For example, some crops have been engineered to produce sterile seeds, forcing farmers to buy new seed every year; other herbicide-resistant strains are produced by the companies that manufacture a particular herbicide, making farmers dependent on buying more and more of one type of herbicide. This is a particular concern to rural economies in poorer nations, where there is widespread scepticism about the potential of genetic modification to ameliorate the world's food crisis. Such controversies have sparked unrest, such as the burning of GM cotton crops by protesting peasant farmers in India. It is uncertain to what extent genetic engineering will gain widespread acceptance, either on the supermarket shelves of wealthy nations, or the farm fields of poorer lands. What is more certain is that this is one of the pivotal debates about the relationship between science, business, and society in the 21st century, especially with the announcement early in 2004 that the UK government gave the go-ahead to one variety of GM maize (for animal consumption), despite the opposition of large sections of the public, the environment select committee, The Soil Association, organic farmers, and concerned scientists.
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