DNA pioneer's genetic make-up published

James Watson, one of the scientists who reported the double helix structure of DNA in 1953, has now had his own genetic make-up completely decoded. A paper published in the journal Nature last week describes the sequencing of Watson's genome to reveal the precise order of all its six billion DNA 'letters'. The project, carried out by scientists at Baylor College of Medicine in Houston, Texas and US company 454 Life Sciences, marks a step towards personal genomics - the routine use of whole genome information in healthcare.

The reference human genome sequence, published in 2003 by an international publicly-funded consortium, took several years to complete and cost hundreds of millions of dollars. But the development of cheaper, faster DNA sequencing technologies - such as that pioneered by 454 Life Sciences - is steadily bringing down the cost of decoding entire genomes. Watson's genome cost about £500,000 to complete, but 454 founder Jonathon Rothberg told the Sunday Times newspaper that the price has now dropped to £100,000, adding 'I'm confident it will have fallen to £1000 within six years'.

However, while sequencing entire genomes is now relatively straightforward, making sense of the information they contain remains a significant challenge. Watson's genome contains about 3,300,000 SNPs - single 'letter' changes in the DNA sequence. Around 82 per cent of these have already been reported, suggesting that the majority of common genetic differences between people are now known. But the effect of most of these genetic variants on a person's health - if any - remains a mystery.

In an article accompanying the publication in Nature, US geneticist Maynard Olson comments that the 'thin clinical value' of Watson's genome 'may cause some investors in the new sequencing methods to take pause', adding 'the major capital investments required to commercialise these technologies have been motivated more by their perceived medical potential than by research applications'. He concludes that the symbolic significance of the paper describing Watson's genome is 'greater than its immediate contributions to human biology'.

The only other person so far to have their whole genetic make-up decoded is J. Craig Venter, the head of US company Celera, which led the rival private effort to sequence the human genome. Venter's genome, pieced together using the 'whole genome shotgun' method previously used Celera, was published in the open access journal PloS Biology in September 2007.