Your genetic code on a disc

Soon everybody could have a personal copy of their complete genetic code, for medical reasons or perhaps curiosity.

A British company says it is close to perfecting a gene sequencing method that could "read" someone's genome in a day.

Meanwhile, Craig Venter - the US scientist who helped decode the first complete draft of the human genome - is reported to be taking orders from millionaires who want to know their genetic make-up.

Dr Venter says he will be able to provide an individual's genome on a CD in about a week for $712,000 (£400,000) from later this year.

The data could reveal whether someone has genes that give them a higher risk of developing diseases such as Alzheimer's. It might even give an idea of how and when they will die.

Cheaper, quicker

The British company, Solexa, was set up by two Cambridge University chemists.

It says it has developed a quicker, cheaper method to sequence human DNA.

This will be used at first to provide a service mapping an individual's single nucleotide polymorphisms (SNPs) - the "letters" of the DNA code that differ between individuals.

These minute differences could explain why some people are predisposed to diseases such as cancer and diabetes, while others are not.

Solexa's ultimate goal is to sequence an individual's entire genome in 24 hours for $1,000 (£562).

Chief executive officer, Nick Mc Cooke, envisages a scenario where you would visit your GP for a blood test and get a complete map of your genetic code.

He says such information could potentially improve human health but must be interpreted properly by a health professional.

"It is possible to contemplate at some point in the future that your complete code is kept confidentially with the rest of your medical records," he told BBC News Online.

"It would shed light on your genetic predisposition to disease and response to certain medications."

Ethical concerns

Genewatch UK, an independent pressure group, says there is an urgent need for better regulation of genetic testing.

"The interpretation of what it means for your future is highly uncertain and often disputed," said Deputy Director, Dr Helen Wallace.

"We wouldn't like to see any company marketing this kind of test until a regulation exists to check whether that test is valid or useful."

The human genome is a string of three billion DNA "letters", comprising all the instructions needed to build and maintain a human being.

The human genome
The genome is the complete list of coded instructions needed to make a person
There are more than 3bn letters in the code in every one of the 100 trillion cells in the human body
If all of the DNA in the human body were put end to end, it would reach to the Sun and back more than 600 times

Two draft versions of the human genome were published in February 2001, in what was hailed as a landmark in scientific achievement.

The effort, which took many years, was carried out by an international public consortium of scientists and a private US company, Celera, headed by Dr Venter, who has now stepped down.

The DNA came from a small number of undisclosed individuals, who are currently the only people in the world to have had their genomes sequenced.

However, Dr Venter recently revealed that his DNA was among the samples used in the Celera work.