Genetic engineering - or biotechnology - is set to become the nuclear issue of the Nineties. The technology involved is as revolutionary as the splitting of the atom, and the effects potentially as catastrophic.

Genetic engineering enables scientists to introduce genes not only from one animal species to another, but also from plants into animals, or from animals into micro-organisms, or any combination of the above. These new biotechnological techniques have the potential to revolutionise both agriculture and the food processing industries.

Genetically engineered animals have already been developed and some, such as the Oncomouse, a mouse used in cancer research, have actually been patented. We can already buy foods, including bread and cheese, that have been produced using genetically modified ingredients. A tomato containing fish genes and one that doesn't rot are also in the pipeline.

Like many new technologies biotechnology is shrouded in jargon. For the non-scientist it may be difficult to find a pathway through terminology like gene splicing and recombinant DNA techniques, yet the implications of genetic engineering are so far-reaching as to touch on every aspect of our lives, from the food we eat to the medicines we take. It is more than a scientific issue, raising moral and ethical concerns that affect us all.

Most of us are aware that our appearance is determined by the genes passed on to us by our parents. Our genes form a blueprint that makes each of us unique and different from any other plant and animal species on earth. Genes are stored in the genetic code which is made up of long sequences of DNA (deoxyribonucleic acid) found in every cell of our bodies.

Traditional breeding techniques have always been able to produce new varieties of animal and plant species by cross-breeding. For example, high milk-yielding cows are bred with other high milk-yielding cows to produce offspring with an even higher milk yield. Manipulating genes in this way takes a long time and results can be unpredictable. Generic engineering is a much more effective way of manipulating characteristics as it will allow traits that would never have occurred in hundreds of years of selective breeding to be introduced in one generation. For example, cows can be genetically manipulated to produce human milk.

Equipped with these engineering tools, scientists can alter the basic blueprint of life. Organisms produced using these biotechnological techniques are called genetically engineered or genetically modified. Genetically engineered animals are called transgenic.

Traditional breeding techniques are responsible for much animal suffering. The modern broiler chicken is already under great stress because it grows so quickly its legs can barely support its own body weight. Eighty per cent of broiler chickens now suffer leg deformities.

The main aim of the genetic engineering of farm animals is to increase so-called 'productivity'. Genetic engineering nearly always imposes pain and distress on the animals it 'creates', both in the laboratory at the development stage and in livestock on the farm. These animals are subjected to severe stress as their bodies are forced to grow faster, bigger or leaner. In the US, pigs have been produced with extra human growth gene: as a result they suffer from arthritis, muscle weakness and poor vision.

Perhaps the best-known genetically engineered product is BST or Bovine Somatotropin. a hormone which boosts milk production by up to 20 per cent. This has been on secret trial in the UK for years. Milk containing BST is added to the general milk supply despite questions about its safety. Cows treated with BST are under severe metabolic stress and suffer increased infection. BST has yet to receive official approval because its benefits are questionable at a time when Europe already has a massive milk surplus.

Claims that genetic engineering of animals will lead to improved resistance to disease and eliminate food poisoning organisms like salmonella and listeria are dubious as genetic engineering could condemn animals to the unacceptable factory farming systems that cause such diseases in the first place.

Another more sinister aspect of biotechnology is the the patenting of animals. Patents are usually granted for inventions, but companies are now applying for patents on animals.

By definition patenting regards animals as objects to be exploited, an attitude that is quite out of step with the modern view of animals as sentient beings. Last year the European Community granted a patent for the Oncomouse, a mouse specifically designed to develop cancer. What possible justification could there be to declare ownership of an animal designed to die from a terrible disease?

Public pressure has successfully stopped the patenting of some animals. Pharmaceutical giant UpJohn was told last November that it could not patent a 'hairless' mouse developed to test hair restorers. This was rejected as immoral because the suffering of the animal outweighed any possible benefit to humanity.

Animals are also being created to function as living 'bioreactors' to produce drugs for human use. For some years biotechnologists have been developing techniques that will turn lactating mammals into pharmaceutical factories. The aim is to produce strains of animals that will secrete therapeutic drugs or proteins into their milk. These proteins can then be extracted, purified and used to treat human disease. Theoretically scientists can produce animals capable of synthesising almost any human protein, provided that the human genes are correctly spliced into the animal's DNA. Some of these products are already undergoing clinical trials, for example sheep have been engineered with a human blood clotting factor gene.

At this early stage in the development of the technology it is patents rather than patients that chiefly concern the pharmaceutical industry. Biotechnology promises to be a major money-spinner as it will enable drugs to be produced at much lower cost.

The experimental insertion of human genes into other mammal species is the beginning of a new chapter in the history of medicine and our relationship with animals. If the technology fulfils its promise, demands on these living pharmaceutical factories will grow rapidly. Existing diseases such as malaria and TB resurface in ever-more infectious forms, and new pathogens such as HIV come along. Moral debate about the introduction of pharmaceutical farming using animals touches on the fundamental relationship of humans with animals. Society rather than science will impose the limits on this new technology.

Medical researchers predict that pigs with human genes will be used as donors for heart and lung transplant operations within 10 years. Already a transgenic pig has been produced which will soon by used in clinical trials.

Biotechnology inevitably means more vivisection. After 14 years of steady decline, 1991 saw the first increase in the number of animal experiments performed in the UK. An extra 35,000 experiments were performed, almost entirely as a result of biotechnology. However many experts argue that the use of transgenic animals as disease models and in safety testing fails to provide an accurate model of human disease while imposing unacceptable suffering on animals.

Gene therapy may bring benefits to people who suffer from serious genetic disorders like cystic fibrosis which would otherwise remain uncured. No one would dispute that genetic engineering has the power to cure disease but the question is how far should we interfere with the very structure of nature's design?

Already there have been some instances of genetically modified organisms (GMOs) being released in this country. The Royal Commission on Environmental Pollution concluded that while most would pose no hazard, some releases could have serious environmental impact. Many of the large insurance companies have already refused to cover potential disasters.

GMOs could become the biogenic polluters of the future. Because they are new to the ecosystem they can spread unrestricted and there is also a possibility of genetic transfer to other species. Scientists are unable to predict what might happen because our understanding of the environment and especially of the workings of soil micro-organisms, is limited.

Other countries are already paying the price for introducing foreign species into their environment, in particular Australia, where thousands of acres have been colonised by a single useless plant species. Genetic engineering promises larger faster-growing crops which will resist insects, viruses, drought and even frost damage.

The major chemical companies are investing heavily in herbicide-resistant crops. These are often resistant to specific herbicides produced by the same manufacturer, which means that farmers are sold a whole package of seeds, fertilisers and pesticides; so increasing the profits and market controls of these companies.

The introduction of herbicide-resistant crops will inevitably lead to increased use of environmentally damaging herbicides and the potential spread of herbicide resistance to weeds by cross-pollination. Herbicide resistance will ultimately prolong the dependency of crops upon chemicals, at a time when we should be moving towards more sustainable methods of agriculture.

The environmental effects of genetic engineering can also be indirect. Salmon can now be engineered to grow to twice their normal size. If these fish were accidentally released into the wild they would consume twice as much food and could upset the ecological balance, driving other species into extinction.

Safety aside, there is also the question of whether it is desirable to continue the trend towards more intensive agricultural practices. Since hungry people need food, it is often argued that making agriculture more efficient must benefit those in greatest need. However, more efficient production means cheaper products and leads to a 'squeezing out' of the inefficient producer - usually the small-scale farmer in developed or developing countries.

While the biotechnology industries continue to claim genetic engineering will help grow more crops to feed the world's growing population, it is clear that they have little to offer subsistence farmers in developing countries.

In addition, biotechnology companies are experimenting with products that substitute those currently produced exclusively in developing countries. For example, vanilla production in Madagascar accounts for ten per cent of the country's export earnings. Research by giant industrial companies is seeking to undercut these earnings by developing tissue culture techniques that produce vanilla industrially. Similar fates await producers of cocoa, gum arabic and sugar which is being replaced by high-fructose corn syrup. Instead of helping to resolve inequalities between the developed and the developing world, biotechnology may exacerbate them.

The genetic engineering of food offers an astounding range of possibilities for the food we eat. The new technology raises ethical issues for both vegetarians and non-vegetarians. Fish genes may be introduced into a tomato to produce tomatoes which sustain less damage when frozen. Most ethical vegetarians would argue that such tomatoes are no longer suitable for vegetarians as fish will have been killed for their genetic material.

The first genetically modified organism to be given formal approval for food use in the UK was a faster-rising baker's yeast. However the customer would not necessarily know if his or her daily bread contained genetically modified ingredients as the UK Food Advisory Committee has so far only recommended the non-compulsory labelling of certain genetically modified foods.

So far the only genetically modified ingredients to have hit the supermarket shelves are a cheese enzyme identical to one found in calves rennet and bread yeasts. The first whole food available could be the Flavr Savr tomato developed by the American company Calgene. This tomato has had the ripening gene removed, so that it does not rot for many weeks after picking.

Non-vegetarians just as much as vegetarians are faced with ethical dilemmas. If the bioreactor sheep with a human blood clotting factor gene found its way on to the meat counter would this make consumers cannibals? Meat from transgenic pigs has already made its way onto the Australian market with no labelling at all, causing a public outcry.

Last year 27 people died and 1,500 became seriously and chronically ill after taking a genetically modified food supplement called L-tryptophan, made by the Japanese company Showa Denko. The drug was not labelled as genetically modified and the side-effects were unpredicted. Are international regulations tight enough to prevent a disaster on this scale recurring?

Food technologists are now proposing to engineer 'designer vegetables', for instance beef-flavoured tomatoes or prawn-flavoured potatoes. The menu of the future could read something like the sinister-sounding offering below.

Genetic engineering is one of the most important ethical issues confronting us today. We cannot allow the political and ethical aspects of biotechnology to remain in the hands of those for whom profit is the chief concern. It is no longer a question of whether scientists will transform life - but to what end.