Well hello, Dolly

The biggest science story of the 1990s was the cloning of Dolly the sheep, announced in February 1997. The news provoked world-wide discussion and controversy, most of it focussed on the possibility of human cloning. This book tells the story of how and why Dolly was cloned. The real importance of this work is quite different from the public perception, and far more interesting.

This book will surely become a landmark publication in this area. The text was written by Tudge, an experienced science writer. Wilmut and Campbell, were the principal scientists of the team that cloned Dolly. Tudge tells the story in a first person style through their words.

The book is beautifully written, following Einstein's advice - `'Explanations should be as simple as possible - and no simpler ". The one quibble I have is the lack of diagrams - I could find only one. More diagrams would enhance the clarity of the presentation for the general reader.

Like every scientific breakthrough, the cloning of Dolly built on the past work of many scientists. The authors describe this work and point out that the primary motivation behind such research was not to produce clones but to understand the mechanism whereby an entire animal, composed of a large number of very different tissues (muscle, bone, etc), develops through a long series of cell divisions from a single fertilised egg cell.

Because every cell in the adult is descended from the fertilised egg, this egg must contain all the genetic information necessary to specify all the eventual differentiated tissues. For many years scientists wondered if different adult tissues each reflect a selective loss of genetic information during differentiation, or a selective switching off of information. Dolly was cloned from an adult udder cell, which means that all the egg's genetic information remains in differentiated cells but much of it is switched off, leaving active only those genes which determine the particular cell type of the differentiated tissue. The Dolly technique re-activates dormant genes in a differentiated cell, allowing the cell to behave like a fertilised egg, beginning the developmental sequence that eventually produces a whole new animal.

The authors emphasise that the main significance of animal cloning is to complete a trio of biological techniques and knowledge - genetic engineering, genomics (comprehensive knowledge of every gene in an animal) and cloning - which will revolutionise biological science and its applications.

Genetic engineering means taking a gene from one organism and inserting it into another. For example, the gene for human insulin was inserted into a bacterium and this valuable hormone is now readily available from this new source. Bacteria are not sophisticated enough to make many other important human biochemicals, but this can be achieved by inserting the genes into animals.

Using the Dolly techniques, isolated animal cells are manipulated to accept a human gene and then cloned to produce new animals that express the gene. A sheep, Polly, was engineered in this way. She secretes human blood clotting factor, used by haemophiliacs, in her milk. A male version of Polly will also be made and will breed with her to produce a whole flock of sheep that secrete this valuable medical product.

The book explains many other developments that will be possible using the new technique: the production of a plentiful supply of animal organs for transplantation into humans; conservation of endangered animals; growing human tissues to replace defective tissues, etc. The authors claim that we are entering an era in which we will exert almost complete control over biological organisms. But this new knowledge will not carry instructions on how to use it responsibly. One thorny issue is human cloning. The authors are against human cloning, principally on the grounds that it would seem impossible to raise a clone as an autonomous individual.

Wilmut's and Campbell's scientific achievement will be forever etched in the annals of biology. However, they haven't allowed fame to spoil them and their personalities come across as decent, unassuming, and ordinary. This is underlined by the fact that neither shone in secondary school. Wilmut failed to get sufficient A levels to go on directly to university and had to do an extra year in secondary school. So, there is life beyond the Leaving Cert.

I recommend this book to everyone who wishes to understand the biological revolution that will affect all our lives.

William Reville writes the weekly Science Today column in The Irish Times, a compilation of which has just been published entitled Understanding the Natural World - Science Today