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The BBC's Fergus Walsh
"Exploring its secrets will take many more years"
 real 28k

Wednesday, 1 December, 1999, 09:08 GMT
Life's 'first chapter' ready for publication
Human chromosomes are bundles of DNA
Human chromosomes are bundles of DNA
By BBC News Online Science Editor Dr David Whitehouse.

An international team of researchers will announce on Wednesday they have reached a milestone in the history of science.

As part of the global effort to map all the genes that form the blueprint of a human being, scientists will publish the entire DNA sequence of one of our chromosomes.

It is chromosome 22 and, according to John Sulston, director of the Sanger Centre near Cambridge, UK, knowing its DNA sequence is akin to reading the first chapter in the book of life.

In the Sanger Centre, and in similar institutions in St Louis, Oklahoma, US, and in Tokyo, Japan, several hundred DNA sequencing machines run day and night, analysing fragments of the human genetic code that have been mass produced in bacteria.

Then a computer looks for overlaps in the DNA patterns so that a complete, unbroken sequence can be put together.

It has taken five years of work to map out the 450 genes on chromosome 22 but this is not the end of the project - it is really just the start.

Medical breakthroughs

Many scientists believe that our knowledge of the genetic blueprint of a human will be the foundations upon which we will build the medical breakthroughs of the next century.

In our genome are the instructions to make all the chemicals and tissues that make a human being work.

Many diseases can be traced to defects or damage to DNA that causes our cells to misbehave. Understanding exactly the molecular basis of disease will eventually provide doctors and scientists with precise details about what is going wrong and send them along the correct path for a cure.

Almost every disease, they add, has a significant genetic component that either predisposes to that illness or protects us from it.

At the moment, such a global view of medicine is just a dream, although the first drugs based on genes sequenced in the human genome project are entering clinical trials.

Our genetic code is found in practically every one of the 100 million, million cells that comprise a human being. Inside most of those cells are chromosomes, coils of DNA that are the templates for the chemicals we need to build and maintain our bodies.

Scientific voyage

Chromosome 22 is one of 24 such bundles and comprises 51 million base pairs.

The gene responsible for the manufacture of myoglobin, a protein important in the transfer of oxygen to cells, is found on chromosome 22. Also, when parts of the DNA on that chromosome swap with DNA on chromosome 9, a form of leukaemia is the result.

"We are learning not just about genes but about how they work alongside each other," says Dr Ian Dunham of the Sanger Centre.

About 95% of the human genome will be read by the end of next year with a complete sequence available towards the end of 2001. Soon, perhaps in less than 100 weeks, we will be able to have the entire human genome put onto one DVD-Rom.

Like the maps of the Middle Ages that spurred the great voyages of discovery, this modern day Mapa Mundi will make possible scientific voyages into the very nature of living things.

It will be the start of another golden age of discovery.

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