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Sumit Bose reports for BBC News
"It's now become a race to find out what makes us human"
 real 28k

Wednesday, 1 December, 1999, 19:04 GMT
Biology's new world
Over 500 genes have been identified Over 500 genes have been identified

It is being described as one of the great landmarks in science.

Biology is entering a new world and facing a revolutionary leap in what we know
Peter Little
For the first time, we have a complete picture of a human chromosome, one of the 46 sausage-shaped structures in cells that bundle up the genetic instructions which make us what we are.

Chromosome 22 is the second smallest of these structures, but it is densely packed with genes which, when defective, are known to contribute to a wide range of diseases and disorders.

Chromosome 22 is involved in the workings of the immune system. It is also implicated in congenital heart disease, mental retardation and several cancers including leukaemia.


Intriguingly, there is also thought to be a gene involved in schizophrenia somewhere on the chromosome.

Finding it could allow scientists to develop new ways of treating the problem. But this will take great effort. The researchers who have been working out the DNA sequence of chromosome 22 for the past five years freely admit that the function of much of the structure is a complete mystery.

They do know that it has 545 functional genes as well as 134 "pseudogenes". The latter are sequences that look like genes but appear unable to instruct the making of a protein. Almost half the genes discovered were previously unknown, and what look like the "patterns" of hundreds more have been picked out in computer analysis.

Major Event

Inside cells
The body has around 100 million, million cells
At the heart of each cell is a nucleus
Inside each nucleus are 23 pairs of chromosomes
Each chromosome comprises a long, coiled strand of DNA
The DNA molecule carries the letters of genetic code, A,T, G and C
Defined regions of the code are called genes and these instruct the cells to make proteins
Our body is built and maintained by proteins
The chromosome 22 sequence is undoubtedly a stunning achievement and one that will rank alongside some of the greatest events in science.

"It's like seeing the surface or the landscape of a new planet for the first time," said Dr Mark Patterson from the science journal Nature which published the scientific paper announcing the breakthrough.

"We knew the planet was there, we knew the chromosome was there, and we knew something about it. We knew some of the genes that were on it for example. But we now have a much more complete and a much more detailed picture."

Dr Ian Dunham, the UK Sanger Centre researcher, who led the Chromosome 22 scientists around the world, said: "The next step is to study the functions of those genes that we found, identify new genes and fill in the gaps in our knowledge."

Future discovery

Dr Michael Dexter, director of the Wellcome Trust, which has helped fund the chromosome 22 work, said: "For the first time the scientific world knows what a whole human chromosome looks like and the knowledge that we derive from this discovery will be used for centuries to come.

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

Dr Francis Collins, who chairs the Human Genome Project, said it was like a dream come true for the disease gene hunter. "A project to find, say, the schizophrenia gene on chromosome 22, which would have perhaps taken a decade to narrow down, should now take only a matter of a few months."

Biochemist Peter Little, from Imperial College, London, UK, said: "Biology is entering a new world; not only do we face a revolutionary leap in what we know, we also face radical changes in the tools we must use to understand that information.

"I am not sure that we are prepared for the full impact of either but we have already made our first tentative steps into the new world of the genome. The challenge is now to translate the new biology into tangible benefits for humanity."

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See also:
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Book of life: Chapter one
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