Bartholomew A. Ochia
Scientists have learned over the last few decades how to isolate genes from various organisms, and transfer them to others, thus modifying the genetic make-up of the recipients. The methods of genetic modification (GM) have elicited unprecedented discussions among scientists and the general public. The explanation for that extraordinary situation can be traced to the nature of the experiments.
One of the techniques used in GM is referred to as recombinant DNA experiment, and it permits the construction in the laboratory of organisms with unique properties which are not known to develop by natural processes. The DNA of plants and animals can be removed and inserted into bacteria and replicated therein; or the DNA of bacteria can be inserted into the genome of animal viruses and then replicated along with the viral DNA. These new capabilities allow scientists to approach previously intractable problems in biology and medicine, opening opportunities in many areas, including the biology of ageing, while carefully avoiding the creation of hazards. Another technique is genetic engineering. This involves the insertion of foreign genes into bacteria, or into cells of higher organisms growing in tissue culture.
In nature gene recombination is known to occur frequently, but that mostly involves genes of the same species. This phenomenon has been used in conventional plant breeding as described below.
Conventional plant breeding
Conventional plant breeding has progressed by leaps and bounds since Gregor Mendel made his famous experiments in his monastery garden in the 19th century. Now, it is becoming complicated. Three main methods are applied. The first is sexual hybridisation. This involves the movement of genes by cross pollination, and results in the production of new gene combinations. To increase the choice of genes, plant breeders have used the ovary-and-embryo-culture technique to hybridise plants, not only from the same species, but also from different genera which do not naturally hybridise. The transfer of genes normally involves several thousands of genes. The difficulty is that when the breeder is only interested in one gene which, say, confers resistance to blight, a lot of time and effort in field selection trials is needed to pin-point offsprings with the wanted characteristics.
The second method, called mutagenic breeding, has been developed to ease the problems encountered in the first method. Plant breeders bombard bags of seeds with radiation or treat them with chemical mutagens in order to induce random changes in the genetic make-up of the seeds. The so-treated seeds are then screened in painstaking laboratory and large-scale field trials to identify rare plants with most favourable characteristics.
The third method is called induced polyploidy, which means multiplying the number of chromosomes in a cell, as is observed during cell division. The chemical colchicine is an extract from the autumn crocus. It can interfere with cell division by inducing the doubling of the number of chromosomes and, as such, the total DNA contained in every cell of the plant. Precaution is taken during test trials; and before a new variety is recommended for use, it has to successfully pass through rigorous selection standards
Doubts about GM technology
The exciting prospects posed by recombinant DNA technology reflect the fact that it provides the ability to combine, at will, genetic information from unrelated species and to perpetuate the recombined genes in easily grown living cells. Undoubtedly, there were, and are still, doubts and scepticisms among scientists and the general public. Does inter-species recombination take place across the species barriers very occasionally, or significantly frequently, among higher organisms? How would genes foreign to any particular cell behave inside it? Therefore, rightly, there is some disquiet that cells containing DNA recombined in the laboratory might acquire new, unpredictable and, possibly, hazardous properties. For instance, under the direction of the new gene a cell could produce a protein not normally found in the host cell, and with undesirable effects either on the host itself, or after release of the protein from the host into human or other ecologically important environments. Furthermore, a host bacterium or virus might serve as a vehicle for carrying the foreign DNA fragment into a human, animal or plant cell in contact with it. If the DNA combined secondarily with the DNA of the new species, the foreign DNA fragment might interfere with normal function; or it might alter the properties of the recipient host cell itself and change, say, benign cells into pathological ones. In plant breeding, what would be the functions of the new gene in the modified plant? Would it induce changes in toxicity or allergenicity? Would genetically modified plants be able to exist in the usual agricultural habitat; and would they have any possible adverse effects on the environment? Could the introduced gene be transferred to other plants via cross pollination and, if so, what would the consequences be? Those were among the fears expressed in the last few decades. However, no known hazardous agent has been produced in recombinant DNA experiment and no genetically modified food crop recommended for human or animal consumption has been conclusively proven to be unsuitable.
Nevertheless, the chance that research might inadvertently cause harm demands responsible action. In the past and present safety procedures have been, and are being, adopted and refined in case things go wrong. Standards for safety assessments have been set up and are adhered to rigorously. Guidelines were developed and promulgated for assessing possible risks and for taking appropriate precautions. Such guidelines were published by government agencies in the UK, USA and other EC countries. In many other countries committees to pro-actively overseer the safe conduct of recombinant DNA experiments were formed. Several international organisations, including the European Molecular Biology Organisation, World Health Organisation, the European Science Foundation and the International Council of Scientific Unions have active committees.
This pro-active approach to safety assessment is commendable, but the only snag, according to Philip J. Dale, is that it tends to make the public more aware of the negative aspects of GM technology than the positive ones. It is thus necessary to promote the positive sides of GM technology; and this is what the concluding part of this article tries to accomplish.
GM and increased world food production.
There is need for increased food production world-wide. Human history has been associated with intermittent crises in regional food supply, culminating in famine and starvation. For instance, in China, where the staple food for the peasants had for long been rice and vegetables, famine has been recorded for over 90% of the period between 108 BC and 1910 AD. Great famines have occurred in India once or twice every 100 years since the past 2000 years. Between 1896 and 1899 there was a moderately severe famine in India, and this was followed almost immediately by a widespread famine which lasted for one year and killed more than 4 million people.
Today malnutrition, i.e., not having enough food to eat, is still considered as a serious international, social, economic and health problem. According to Food and Agricultural Organisation, the proportion of the world population who are malnourished has decreased gradually for the last few decades; however the absolute numbers are not yet, seemingly, declining. According to A.J. McMichael, the number of the world’s malnourished was 830 million, of this 790 million was in developing countries.
Most international agencies optimistically foresee that future food production will match increases in world population size and rising consumer demands for the next two or three decades. After that period there will be a worsening food security especially in sub-Saharan Africa; and in South Asia food supply will only be marginally improved. It appears obvious that the cereal-grain producing countries, such as Argentina, Australia, Europe and North America will have to redouble their efforts to satisfy the demands of the developing countries as their population continues to increase.
In 1900 world population was 1.5 billion; by the year 2050 the estimated figure will be 9.0 billion. At present, modernisation of agriculture, improved food distribution and trade as well as international food aid have all combined to cushion the impact of local or regional famines. But mankind still faces the unpalatable prospect of population size exceeding food supplies, as factors such as global climate change might deleteriously affect world food production and consequently produce local famines. There is, therefore, good reason to believe that every avenue should be explored that leads to increased food production.
Our capacity to satisfy the food demand for increasingly large world population calls for maximising the efficiency and sustainability of production methods which incorporate socially beneficial GM engineering. This technology offers tremendous potential for the present and the future in the development of new crop varieties which are highly nutritious, resistant to pest attack and able to flourish in unfavourable environments. Already GM crops have become an important part of world agriculture. In 1999 about 40 million hectares of them were grown throughout the world, with the largest area grown in the USA, followed, in decreasing order, by Argentina, Canada and China. The Chinese, in particular, have embraced GM technology enthusiastically, not least because of their country’s history of famines. The trend in many developing countries is towards increased use of GM products.
Modification of genes occurs continuously, albeit imperceptibly, in nature. This results in the formation of new varieties, species and, even, genera of animals and plants. Mankind has been able to interfere with nature to his/her advantage. So, the current efforts by scientists to manipulate genes, in order to produce plants with increased yield and high nutrient contents, and able to thrive in hostile environments, should be accepted as a normal progression in the quest of mankind for advancement. Men and women are living longer, and the race is on among scientists to find cures for the many illnesses associated with old age. Recombinant DNA technology will help to pin-point those genes responsible for those disorders, and make it possible for most people to age without losing their vitality and ability to enjoy life. To assuage the fears of those sceptical about genetic technology, there are the safety standards and binding regulations for scientists to follow. GM technology has a major role to play in global food production in the future.
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