BOOK REVIEW / Awaiting the shock of the new genetics: The engineer in the garden - by Colin Tudge: Cape pounds 17.99

TO MOST people, the idea of genetic engineering probably conjures up images of misbegotten monsters, like Vincent Price's head joined to an insect's body in The Fly, or the horrible man-pig glimpsed briefly in Lindsay Anderson's O Lucky Man. It is unlikely, however, that public knowledge will remain at this cinematic level for long, for in the next few years genetic engineering promises to transform modern life as much as the aeroplane and the computer have done.

Colin Tudge's new book is intended to prepare his readers for this coming revolution. For the most part he succeeds admirably. Tudge is a distinguished science correspondent who has written widely on agriculture and conservation, and the first half of The Engineer in the Garden could not be bettered as a popular introduction to genetic knowledge. Tudge is especially good on how the structure of our genes has shaped the course of evolution and made possible the achievements of conventional agricultural breeders.

Tudge is also helpful on the basic chemistry of the new genetic engineering. Talk of scientists 'snipping out' strands of DNA, and 'stitching them' into the DNA of other organisms, can often seem mystifying, given that DNA strands are roughly a millionth of a centimeter thick, and not the kind of thing you can manipulate even with microsurgical scissors and needles. But Tudge explains how biotechnology uses nature's own tools to perform these tricks. Bacteria contain enzymes whose job is to kill invading viruses by severing their DNA. Modern biotechnologists have identified where these enzymes make their cuts, and how the resulting fragments of DNA will recombine. This enables them to orchestrate their magic just by shaking up the right ingredients in test tubes. The Engineer in the Garden is less satisfying on how these new techniques will matter to our lives. This is not really Tudge's fault: no one can predict how new technologies are going to be used. What normally happens is that the engineers create possibilities, and then someone like Alan Sugar sees what people want to do with them. When microcomputers became available at the beginning of the 1980s, everybody agreed they were jolly useful, but nobody was quite sure what for. A lot of nonsense was written about how we would soon all be cooking and washing by computer. But I don't remember anyone saying then that they would make typewriters obsolete within 10 years.

The commercial uses of the new biotechnology are still in their infancy. Genetic engineering has already made contributions to medicine, but for the most part its potential applications are still at the development stage. Tudge describes much of this work-in-progress, but his prognostications of insect-eating hedges and self-growing steaks inevitably have a tinge of hopeful speculation.

The dangers of genetic engineering are easier to identify than its benefits. High on the list are the monstrosities of popular imagination. These mightn't be the graphic chimeras depicted in the cinema, but farmers will certainly want to use the new techniques to exaggerate profitable traits. Tudge tells of plans to produce chickens who lack nerves to their beaks, so that they will not feel pain when they are 'de-beaked' to stop them pecking each other in batteries.

This is of course a horrible scheme, but, as Tudge points out, it is scarcely rational to blame the new biotechnology. After all, farmers already raise chickens in batteries and cut off their beaks, despite the pain this undoubtedly causes them. The new genetic techniques may lead to new kinds of unhappy animals, but it will be building on a long tradition of pigs that cannot stand, turkeys that are too large to mate and beef calves with such exaggerated muscles that they have to be delivered by Caesarean section.

The same point applies to the danger that some newly engineered organism may escape from the laboratory and lay waste to the environment. This is certainly a genuine threat, but it is scarcely a new one. We didn't need to wait for recombinant DNA to discover what kind of damage the cane toad, the mink or the rhododendron can do in the wild.

Even so, it is thin consolation to be told that genetic engineering only gives us new versions of old problems, given how badly we have already fared with the old versions. Tudge recognises this, and argues that a healthy relationship with nature will only come when we have adopted a less aggressive attitude towards its exploitation. But he is not over-optimistic about this change. Biological science now offers us a battery of sophisticated techniques which were unimaginable a few years ago. But it will require a different kind of sophistication to know how to use them well.

(Photograph omitted)