The basic principle governing genetic engineering is that genetic material which is also known as DNA can be transferred from a cell of one species to another unrelated species and made to express itself in the recipient cells. This is also known as recombinant DNA Technology.
Mother nature is the first genetic engineer who has been experimenting on newer and newer life forms over billions of years. We have only very recently started modifying the genes, which are the ultimate code of life. There are innumerable instances where we have successfully applied the techniques of genetic engineering. For example, scientists have now identified defective genes that cause diabetes and in the years to come, genetic engineering may offer simpler solutions to treat diabetes instead of life long treatment usage. In the last decade, genes from bacteria or viruses have been inserted into DNA or genome of the host crop so that it develops better resistance to diseases. This idea gave rise to several genetically modified crops which are presently invading the global market.
Genetic engineering knows no boundaries. The genes of one species can be conveniently introduced into the other species with a definite purpose. In most cases, these experiments are carried out for positive results, either to increase the yields of crops or to promote better health. However, doubts are being raised over the very process of experimentation.
The promise of gene technology is the stuff that science fiction is made of: Bananas that vaccinate a child against measles; maize that can grow in Africa's patched soils and survive drought conditions, or even an orange that can prevent cancer - all these are the possibilities in genetic engineering. The aim of this new technology is to give the recipient species a new trait such as the ability to resist herbicides and pesticides, or to grow in abnormal climates like the deserts of Africa. Scientific Think-Tanks involved with biotechnology giants of the world are poised to surprise the world with many such experiments in the years to come.
Proponents of genetically modified foods, including many agricultural and nutrition scientists, are of the opinion that GM foods could help fight hunger and malnutrition. Several other scientists, environmentalists and consumer activists opposing this technology opine that GM foods will destroy the environment, make people sick and hand over the control of world's food production to the hands of a few multinational corporations. The critics say that GM foods have been channeled into the food chain at a pace that has outstripped the ability of governments to either regulate them or address the concerns of opponents. And this according to them means that one of the most important ecological safeguards to protect the environment and enforce our constitutional rights has been sacrificed in favour of expediting the application of this technology.
Cultivation of GM food crops
In the last century, a variety of different breeding approaches have been used to improve crop production and quality, but it was not until the early 1980s that a new and powerful technology, “genetic modification”, was developed. This technology had not only transformed the agricultural industry but had also created a gulf between companies wanting to exploit the new technologies and critics who believe that GM foods are inherently unsafe to both environment and public health.
The first ever transgenic crop was produced in 1983 followed by the first outdoor field trials in 1987. The first GM plant commercialized in China in 1992 was a virus-resistant tobacco plant which was followed two years later by the first GM plant (tomato-based) food product. By 1996, 23 GM crops in US, 12 in Canada and 7 in Japan, had been approved for commercial production. North America is an example of excellent market for GM crops. In 1996, it started with growing GM crops on only 2 million hectares (ha). increasing to 8.1 million ha in 1997 and to 20.5 million ha in 1998.
Advantages
GM technology is preferred to traditional breeding techniques as it is much faster and cheaper and allows a greater precision in selecting desirable characteristics. Some of the important benefits of this technology are:
-
Pest resistance: A gene that naturally occurs in the said bacterium, Bacillus thuringiensis (Bt), produces an insecticidal protein that interferes with the ion transport system, disrupting an insect's ability to feed. Plants carrying the inserted Bt gene are able to produce Bt protein protecting themselves against targeted pests. In addition to requiring less insecticide for effective protection, the modified crops possesses improved yield and quality traits.
-
Herbicide tolerance: These modified crops provide farmers with greater flexibility in herbicide use and reduce or eliminate the need for pre-emergent soil applications. The first genetically modified soy product has been already commercialized and products relating to cotton, corn, sugar beet and oilseed rape are currently under development.
-
Virus resistance: China was the first country to commercialize virus resistant transgenic crops with the introduction of virus resistant tobacco in 1992.
-
Improved quality: Delaying the onset of ripening by suppressing polygalacturonase, the cell-wall degrading enzyme in tomatoes, allows the fruit to stay on the shelf for longer duration and develop a better flavour and colour.
-
Nutritional improvement: Attempt to incorporate specialty oils, carbohydrates, proteins and other value ingredients into common crops have also been tried with some success. Most of the research was carried out on edible oil modification and several GM crops have been developed with improved quality. Genetic modification of oilseeds resulted in products yielding high oleic acid (18:1) low linolenic acid (18:3) increased lauric acids and larger yields of many edible oils. Canola oil with high lauric acid content, soy beans with high olelc acid, β-carotene and iron-rich rice variety, rape seed oil with low levels of saturated fatty acids are some examples in the case.
Apart from increasing the nutritional quality, genetic modification is also used to prepare high stability oils which contain high oleic acid content. These high stability oils can be prepared without chemical treatment, by eliminating trans-fatty acids and by improving the actual oxidative stability without the addition of tocopherols.
-
Adaptation to harsh conditions: Genetic modification can help the crops to grow in harsh conditions like drought, temperature extremes and soils with high salt content.
-
Seed proteins: Soybean and canola seed storage proteins are deficient in methionine. Scientists have taken a gene from Brazil nut that encodes a 2s storage protein with a methionine content of 18% and introduced it by transformation into canola. It led to an increase in net content of seed meal by more than thirty percent. However, search is on for a better alternative to Brazil nut as there are certain problems in its usage.
-
Breakthrough in the development of Neurotoxin-free Lathyrus sativus: L.sativus, a grain legume, has a unique feature of tolerance to drought and flood conditions. Its cultivation is banned because of the presence of a toxin, BOAA. This toxin causes a neurological disease called Lathyrism. This gene has been isolated from Pseudomonas strains which can effectively degrade the BOAA toxin and render the pulse harmless for human consumption.
Issues of concern
There have been various concerns highlighted in recent years regarding the safety of GM foods. Many of these worries are speculative with little or no scientific evidence to back them up, while a few have created wide debates among scientists and general public. These main concerns include antibiotic resistance, allergenicity, potential toxicity and environmental issues.
Antibiotic resistance
Antibiotic “marker gene” are commonly used to trace the gene transfers. All genetically engineered products have antibiotic marker genes. After GM food is absorbed into the human digestive tract, these antibiotic genes could move from what we have eaten into the blood stream or into the bacteria harbouring the intestine. Such transfers might affect our health directly or affect the symbiotic relationship between us and the intestinal flora. Consequently, we may develop resistance to several antibiotic drugs leading to a major public health problem.
But a major concern is whether the transfer of antibiotic resistance (trait) from a marker gene in plants to a micro-organism naturally present in the human gut or harmful bacteria is possible. Currently, there are two examples where clinically important antibiotics have been used as a marker system in crops. The first is a maize variety that contains a gene for ampicillin resistance and the second is a potato variety that contains a gene for amikacin resistance. Although this has not been demonstrated experimentally, any risk, no matter how small, of spreading resistance to therapeutic antibiotics should be avoided.
The UK's ACNFP (Advisory Committee on Novel Foods and Processes) in the absence of reliable data, has erred on the side of caution and has recommended that Antibiotic Resistant Marker (ARM) genes should be eliminated from GM microorganisms which have not been inactivated by processing, for example, bioactive yoghurts. However, a recent attempt by ACNFP to ban an unprocessed animal feed produced from GM cotton seed containing an ARM was overturned at the European level by Scientific Committee for plants.
Allergenicity
Another public health concern over human consumption of GM foods is that some percentage of the public may be allergic to a protein coded by the gene introduced into GM food. Allergic reactions can either he extremely mild or quite dangerous. According to one estimate, the past decade has seen a 300% increase tn allergies around the world. Exposure to new foods can reveal new allergies and the combination of genetic material can lead to “cross-allergenicity”, where people allergic to one thing may be allergic to the genetic material that has been added to an item they once ate safely. It means to say that if a person is not normally allergic to potato but say to brinjal and if a gene of brinjal is inserted into the genome of the potato, then the person eating that modified potato may also develop allergy to potato. In the present scenario, consumers with certain food allergies would not be able to decide whether to choose or to avoid GM foods. So, the present demand is for labeling of GM foods in which the details pertaining to the organism used for modification are also furnished.
Potential toxicity
The possible production of toxic compounds in GM foods or the production of harmful metabolites from GM fermentation microorganisms is another concern. An example of this scenario is demonstrated by the research conducted involving inserting of lectins into potatoes. Lectins, a complex plant protein, are inserted into plants as a means of enhancing pest resistance, but when inserted into potatoes, they were shown to have an adverse effects on rats during feeding trials. However, it was later found by scrutinizing agencies that the experiments were poorly designed.
Environmental concern
Past experiences with the introduction of new species into the environment have already demonstrated that potential problems do not manifest themselves immediately but take several generations to become apparent. There are fears of genetic drift, where, for example pollen from one kind of plant is taken up by another plant. Similarly, genetically engineered traits such as herbicide-resistance may spread to weeds leading to the creation of indestructible weeds immune to herbicides.
For example, in April 1999, the UK's National Institute of Agricultural Botany, reported that a hybrid superweed may have been created after some GM canola pollen was taken up by wild turnips. These turnips subsequently showed resistance to the herbicide to which canola was made to be resistant through genetic engineering.
It has been suggested that the adoption of insect-resistant crops will disrupt the food chain and lead to the extinction of insect species thereby reducing biodiversity. There is also the potential problem of cross contamination from GM crops to non-GM crops resulting in a loss of authenticity for organic farmers, who will no longer be able to classify their products as 'organic'.
Legislations and labeling requirements
The concept of labeling is based on the condition that if providing a new food is substantially equivalent to an existing food or component then it can be treated in the same way with respect to both its safety and nutritional characteristics. Therefore the acceptability of a GM food is determined by its comparison with an analogous conventional food in terms of composition, toxin and allergen content nutritional properties, metabolic fate and intended use.
Despite many people considering the use of substantial equivalence as an insufficient means for regulatory control of GM foods, many countries including Canada and the US, still rely on it. However in UK, the concept of substantial equivalence was redefined in December 1997. Only highly processed food products derived from GM crops such as white sugar and hydrolysates, which are unlikely to contain DNA or protein, are considered substantially equivalent to their counterparts, while all other ingredients derived from GM crops such as flour and protein require a full safety evaluation.
The food labeling laws are different in different countries. The European Union argues that any food containing detectable amounts of GM ingredient should be labeled as such. Some countries such as India, Norway and Denmark have gone a step further and called for all foods produced using GM technology, regardless of the presence of GM ingredients in the final product, to be labeled accordingly.
In contrast, US argues that this is not only unnecessary, costly and complicated, especially if ingredients are taken from a number of sources but that it also implies that GM technology is inherently unsafe when there is no direct evidence to substantiate such a conclusion. However the US argument fails to address two important issues which are the need for public acceptance of GM technology and more importantly to allow consumers their fundamental right of choice. In fact, the outcry against GM foods did not start until it became public knowledge that GM soy was being mixed with non GM soy in America and exported to Europe, where around 60% of processed foods contain soy protein.
Analytical methods for detection and quantitation of GM foods are basically needed for the food labeling laws and for the food safety evaluation.
Some of the methods which are now being used include Immuno assay, PCR analysis and Antibody based lateral flow test strips.
Out of these, immuno assay is more simple and PCR analysis is more sensitive. By using these techniques, we can also detect the percentage of genetic modification present in the crops.
What does the future hold?
Rapid strides are bound to be made in the field of GM foods in the coming years. These areas include:
Plant Biotechnology
In future, Plant Biotechnology might help us to grow :
-
environmentally hardy food-producing plants that are naturally resistant to pests and diseases and are capable of growing under extreme conditions of temperature, moisture and salinity
-
fresh fruits and vegetables with excellent flavour, appealing texture and optimum nutritional content, that stay fresh for several weeks.
-
custom designed plants with defined structural and functional properties for specific food processing applications.
The diet-health interface
It will be possible to get
-
engineered meat with reduced saturated fat or eggs with decreased cholesterol
-
milk with improved calcium bio-availability, and
-
cereal grains with increased levels of specific components that mitigate or even prevent diseases viz. soluble or insoluble fiber, omega 3 fatty acids, beta carotene or selenium.
Food-grade micro-organisms
In future, biotechnology might hold for us in a way that
-
Cultures are programmed to express or shut off certain genes at specific times during fermentation in response to environmental triggers.
-
Strains engineered to serve as delivery systems for digestive enzymes for individuals with reduced digestive capacity.
-
Microbially derived high value, natural food ingredients with unique functional properties
Conclusion
Despite the global trend in growth, there has been substantial resistance to GM technology in Europe, where currently there are no GM crops licensed for either commercial production or consumption. Presently, there are no GM crops cultivated commercially in the UK and it is unlikely that there will be until near future. In fact, UK has only 4 GM foods that have gained full approval and are in commercial use. These include cheese produced with a GM chymosin, tomato paste produced from slow softening tomato, GM soy and GM maize.
Despite many advantages genetic engineering can offer to food industry, public concern regarding this technology still remains high throughout Europe, although attitudes towards accepting it have improved in America and Asia. Many argue that labeling all foods produced by GM technology is the only way forward to regain the support and trust of consumers. Perhaps, this is a small price to pay if this technology is to make an impact in the 21st century. However, one thing is certain and that is if this technology is to succeed, the preferences and requirements of the consumers need to be addressed by governments, scientists and Industries alike.
References and sources:
This article has been collated from print material (magazines and publications) and internet resources which were not noted at the time of writing.
