The human puzzle

It has undreamed-of implications for virtually every aspect of our lives. Medicine, agriculture, biology and forensic science will never be the same again. In future the data may make it possible to banish inherited disorders, screen people for their vulnerability to disease, tailor treatments to the individual's genetic make-up, create thousands of new drugs and repair faulty genes.

It could, in short, immeasurably improve human health and prolong human life.

But Professor Norman Maitland, head of a team at York University leading the search for a cure to prostate cancer, warns that decoding the three billion chemical 'letters' in DNA - our genome - is just the beginning of the story, not the end.

And while the potential benefits of the new knowledge unlocked by scientists in Britain, Europe and the United States is vast, there are dangers too.

All we have at the moment, Prof Maitland points out, is a list of 'letters'. Scientists have still to learn to read them. "It is the same amount of letters as there are in eight Bibles," he said. "There's the old saying: if you give a monkey a keyboard, he will eventually be able to write Shakespeare. Well, we're not quite at that stage: but we have a tremendous amount of sifting to do."

That sifting will involve trying to work out how the DNA 'letters' combine to make genes - the building blocks of life. Sequences of several thousand letters along the DNA strand make up a single gene. Trying to identify individual genes is like trying to read a book eight times as long as the Bible in which all the letters are spaced the same distance apart, so there are no spaces between words, no punctuation, no paragraphs or chapters.

Even once that is done, Prof Maitland points out, we won't have anything like the full story. All we would have is a 'generalised' map of the human genetic code: whereas in fact every individual has a unique map that differs from every other. And anyway, he says, there is more that goes into making a human being than simply our genes: there is the small matter of our environment - diet, education, lifestyle and the way we're brought up and so on.

Still, the cracking of the genetic code is 'terrific news' which could have massive implications for the quality of life of future generations of human beings, Professor Maitland says.

By understanding the chemical 'switches' which controls genes scientists in future, he says, may be able to 'switch off' in particular individuals the genes that produce harmful proteins, causing conditions such as cancer and heart disease. Understanding of inherited conditions such as cystic fibrosis, muscular dystrophy and haemophilia will also be greatly improved.

There are also risks and ethical dilemmas associated with the new knowledge.

Ethical decisions will need to be taken about whether to inform someone that they or their children are susceptible to a life-threatening disease. In the hands of insurance companies, that information could push up premiums payable by those who are susceptible. There will also need to be an ethical debate about the merits of engineering the genetic makeup of adults to ensure their children do not inherit diseases from them - effectively breeding a new 'super-race'.

"There may well need to be a whole new breed of scientists, genetic ethicists, who will help people make these decisions," Prof Maitland says.

Most important now, though, he says, is that the benefits of our new understanding of the 'book of life' should be available to all. There are already worrying signs that commercial companies which joined the gene hunt may attempt to 'patent' gene sequences they identified for sale to industry.

"I just hope that this information is used for the benefit of mankind rather than to earn lots and lots of money," Prof Maitland said.

picture- A representation of the double-helix strand of DNA