The Gene Dilemma: Plants and animals yield new foods and drugs: Human genes are being slotted into vegetables and fish genes into fruit. Susan Watts reports

THE NEW GENETICS is not confined to work on human DNA. Scientists can now manipulate the genes that form life in a vast range of plants and animals - producing new foods, drugs and crops.

Gene transfer knows few limitations - scientists can slot human genes into vegetables and fish genes into fruit. Genetic engineers have produced crops that resist pests, disease and frost, stay fresh longer and taste sweeter.

Food technologists have produced tomatoes that stay firm, and others with a gene from flounder fish that renders them frost-resistant. Biotechnology companies in the United States have produced peanuts, cucumbers, potatoes and tomatoes that resist viruses.

A joint French, British, Spanish and Greek project is developing the 'Euromelon', with an artificially extended shelf-life. The Safeway supermarket chain is funding work on iceberg lettuces to produce individual serving- sized heads. McDonald's and Du Pont are working on celery and carrots engineered to stay crisp for pre-cut snacks.

Technologists in the US are working on low-fat chips from potatoes with an extra gene taken from intestinal bacteria. This gives them a higher starch content, so they absorb less water when fried.

The pharmaceuticals industry stands on the brink of a genetics revolution, both in understanding disease and producing drugs to counter it. 'Transgenic' animals have become sophisticated tools for medical research - with extra genes that turn them into living models for diseases. Engineered mice can develop enlarged prostate glands, mimicking a common disorder in men.

Researchers in the UK have developed mice prone to thromboses and diseased heart muscle, and transgenic animals such as pigs are being developed with hearts their creators hope will prove suitable for human transplants. Sheep, rabbits and mice have become biological factories, with extra genes that produce drugs in their bodies. An Edinburgh company, Pharmaceutical Proteins, has developed sheep whose milk contains a blood-clotting factor and a drug for treating emphysema, the lung disorder.

Others are trying to insert a human gene into mice so they will produce beta interferon, a protein useful as a drug since it attacks viruses and prevents infection.

Agricultural scientists are working on livestock that will be easier and cheaper to manage, such as disease-resistant farm animals with leaner meat. Researchers at Ohio University have produced a strain of mini-mice, half the normal size, which they say could lead to smaller farm animals.

Commercial ventures have applied for hundreds of patents on such 'inventions'. The University of California wants to patent animals given defective cancer suppressing genes, useful for testing the carcinogenicity of tobacco and food additives.