Scientists `read' chromosome in first for medicine

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SCIENTISTS SAID yesterday they had passed a milestone in medicine by cracking, for the first time, the DNA code of a human chromosome.

Hundreds of hitherto unknown genes have been revealed because of the breakthrough, which involved reading the complete sequence of 34 million "letters" that make up the genetic code of chromosome number 22 - one of the smallest of the 23 pairs of human chromosomes.

The painstaking work marks the first time that a human chromosome has been sequenced in full and the fruits of the work would continue to be used in a thousand years' time, the scientists said.

Ian Durham, who led the team at the Sanger Centre in Cambridge, collaborating with scientists in America and Japan, said the publication of the sequence in the journal Nature after nearly a decade of work came as a great relief.

"This is the first time we have been able to see a whole human chromosome in this detail, the organisation of the genes and how they relate to each other," Dr Durham said.

Michael Dexter, director of the Wellcome Trust, the research charity that funds the Sanger Centre, said the breakthrough provided a model for the completion of the entire complement of 23 pairs of chromosomes, expected by 2003.

"It is a remarkable achievement that will change the way in which diseases and other medical conditions are diagnosed and treated," he said.

The researchers acknowledged the pioneering developments of Fred Sanger, the British biochemist who won two Nobel prizes during his time at Cambridge's Laboratory of Molecular Biology.

Dr Sanger, 81, said yesterday that in the mid-1970s there was almost no contact with the patients who might eventually benefit from the gene research.

"It's very exciting to me that it is becoming of practical interest and there is a chance of doing some good for humanity," Dr Sanger said. "I think I dreamed about it, but I didn't really believe it."

Deciphering chromosome 22 has already uncovered 679 genes - including those implicated in leukaemia, schizophrenia and mental retardation - of which 55 per cent were previously unknown. The final tally of genes could be nearer 1,000.

Michael Morgan, chief executive of the Wellcome Trust, said all the sequencing information was being made freely available to academics and industrialists.

John Sulston, director of the Sanger Centre, said the international collaboration that led to the discovery could only have occurred with free availability of data. He criticised private organisations, such as Celera, a biotechnology company in Maryland, which does not share gene sequences freely without making a charge.