Beyond grey goo

Picture a test tube whose murky contents can near-instantaneously decrypt a protected email which would keep today's most powerful computers occupied for months; another that could tell you the most efficient journey plan for visiting the US's 50 largest cities; an organic implant that diagnoses and cures cancer before any symptoms show. They may all be impracticable at present, but given how unpredictably scientific advance moulded our last century, we should assume that the biotechnologies which this book so engagingly introduces will have effected similarly radical changes on us by the end of our present one.

Martyn Amos holds the rare distinction of having been awarded the world's first PhD in his chosen field, DNA computing, and Genesis Machines is his eye-opening presentation of this young science to the lay reader. Attacking our preconceptions, Amos briskly surveys the history of computing from Descartes to Turing and beyond, demonstrating that the concept of "the computer" is a question to which our ugly silicon, plastic and metal boxes are not the only answers.

True, the pace of their development has been jaw-dropping, but it pales into insignificance next to the implications of our recent understanding of the molecules of DNA and the enzymes which act upon it. Indeed, if the book has a hero, it is DNA, whose four bases (A, G, C and T) have powerful properties - notably their tendency to bond to each other in predictable and manipulable ways.

And if you need a human hero, then it may be Len Adleman, the American polymath who was among the first to realise the resemblance between the DNA chain and Turing's theoretical information strings - a foundation of modern computing. (This was in 1983, shortly after he invented the cryptography that secures your internet shopping, and around the same time as he coined the phrase "computer virus" - quite a chap, this Adleman, it seems.)

It is hard not to share Amos's excitement as the computational possibilities of the DNA revolution become clear. There are back-of-the-envelope ideas as beautiful in their simplicity as they are staggering in their implications. One such, as an accidental by-product, gave us the method by which single DNA strands can be duplicated in the lab (thus revolutionising forensic science); another generates solutions to simple versions of the journey-plan problem mentioned above. It's disappointing when it becomes clear that pots of DNA will not supplant the PC: real-world journey plans would need "a set of DNA strands that weigh more than the earth" to compute.

So much for biocomputing outside DNA's natural home, the cell: intriguing, but limited in its practical implications. It is more likely that its computational powers will instead be put to service in the body, listening to the traffic of organic molecules and responding to signals of dysfunction with tailor-made therapies. This might, perhaps, involve "switching" our own genes on or off, or creating molecules to trim the DNA of malfunctioning cells in a tumour. Outside the body, bacteria might be created that would glow in the presence of a given toxin, thereby alerting us to its presence.

All this is chattily recounted: Amos happily supplies personalities for the non-specialist reader to connect with. There is the odd un pleasant racist, a conjuror whose lectures on bacterial genomes feature the Indian rope trick, a couple of difficult geniuses, and a parade of amiable Californians. We learn of their lives and loves, the practicalities and pitfalls of academic publishing and the torture of having an earth-shattering idea in a weekend cabin miles from the nearest phone. More importantly, Amos makes the science accessible, with well-plotted and nicely structured explanations. It's clear that this field will continue to throw up dramatic advances, even if we don't quite know what, yet: as the estimable Adleman happily points out, Columbus "was looking for India, and he smacked into America". Genesis Machines provides a fine introduction to those wishing to follow its progress.

This article first appeared in the 04 December 2006 issue of the New Statesman, Nation of fools