(Agencies)
Updated: 2008-03-31 09:27

In practice, genome scans can be big undertakings.

Scientists in Iowa and Denmark are searching blood samples from 7,000 babies and new mothers in the United States and Denmark for genetic variations that raise the risk for premature birth.

DNA will be extracted, and early this summer, more than half a million spots on the microscopic strands from each mother and baby will be assessed for clues to where the genetic variations may lie.

The DNA will be analyzed at the Center for Inherited Disease Research at Johns Hopkins University in Baltimore. Robots will put a tiny drop of DNA-bearing solution from each person onto a clear glass slide roughly the size of a business card, with four drops per slide.

The lab's DNA scanners, blue boxes each about twice as big as a desktop printer, will reveal what DNA "letter" appears in more than 580,000 spots in the genetic material, said lab director Kimberly Doheny.

This scan takes about half an hour per sample. Once the results are available, the scientists will use statistical tests to find the telltale signs of a possible gene affecting risk of premature birth. They'll double-check to make sure any such signal shows up in more than one population.

Even five years ago, such a detailed examination of DNA from so many people would have been inconceivable.

Genome scans offer some major advantages over previous gene-hunting techniques. Scientists don't have to start by guessing what genes might be involved in a disease, or confine themselves to families where a tendency to an illness is inherited.

And the genome-scan approach reveals genes with only subtle influence on the risk of getting sick, too slight to be found by earlier methods. That's just the kind of gene that plays a role in common illnesses like heart disease.

Even if its impact on risk is small, a newly found gene can be a bonanza to scientists if it reveals something new about the biology of a disease. That in turn can give hints for finding new treatments.

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