New Cheaper Method For Mapping Disease Genes

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New Cheaper Method For Mapping Disease Genes

http://medicalnewscenter.com/out/out.cgi?

http://www.sciencedaily.com/releases/2008/05/080526165347.htm

Scientists at the Swedish medical university Karolinska Institutet

have developed a new DNA-sequencing method that is much cheaper than

those currently in use in laboratories. They hope that this new

method will make it possible to map disease genes in large patient

groups, which in turn can mean quicker breakthroughs for new

treatments for a wide variety of diseases.

By mapping DNA, scientists can trace disease genes, understand how

bacteria and viruses cause infection and chart the evolution of

mankind and other species. When the HUGO project mapped the first

human genome not so long ago, it cost over a billion kronor and took

over ten years. Today, there are instruments on the market that can

do the same thing in a matter of months for less then ten million

kronor. However, if scientists are to have opportunities to study

disease genes in detail, and from hundreds of patients, the process

must be much, much cheaper.

A Swedish team, led by Sten Linnarsson at the Department of Medical

Biochemistry and Biophysics at Karolinska Institutet, has now

developed a new DNA-sequencing method that can one day make it

possible to map out the human genome for one-tenth of today's cost.

The method is presented in the online edition of the scientific

journal Nature Biotechnology.

The scientists took DNA from the enteric bacteria E. coli and split

it into tiny fragments, each with a length of approximately 200

nucleotides (the building blocks of DNA: A, C, G and T). These

fragments were then spread out and fixed onto a microscope slide so

that several million fragments could be analysed simultaneously.

These fragments were then rinsed in a fluid containing short DNA

sequences of five nucleotides, marked with a fluorescent dye, which

allowed them to examine which of the short DNA sequences adhered to

each fragment.

After having rinsed all possible short DNA sequences over several

million fragments, the scientists were able to then digitally piece

together the sequences into one complete chain of the entire bacteria

genome, a total of 4.5 million nucleotides long.

" Everything takes place in our own specially built instrument, which

comprises a microscope powerful enough to take pictures of DNA

fragments, an automated pipette and a small flow chamber with a glass

surface on which the reaction itself occurs, " says Sten Linnarsson.

This is not the first time that Swedish scientists have successfully

developed new methods of DNA sequencing. Ten years ago Pål Nyrén and

his colleagues from the Royal Institute of Technology published

Pyrosequencing, one of the most common methods of mapping DNA in use

today.