Utah: the perfect genetics lab: big families, Mormon Church records, and even 19th-century polygamy are proving a boon to the study of genes and genealogy.

Utah is famous for its big families, with seemingly endless branches of aunts, uncles, and cousins, and roots stretching back to Mormon pioneer days. But what once appeared to be a regional quirk is increasingly viewed by scientists as something more: a near-perfect laboratory for the study of human genetics.

Utah DNA is being used for an international study that seeks to identify chromosomes linked to diseases like asthma and diabetes. Other researchers are studying how the genes for left-handedness or longevity have moved through the Utah gene pool over time.

A foundation in Salt Lake City is compiling a giant genetic database that will be used to pinpoint where a person's ancestors came from, using a sample of DNA. "Utah's contribution to genetics has been enormous," says Mark S. Guyer of the National Human Genome Research Institute in Maryland.

To a scientist, the greatest attraction of Utah is stability. For more than 150 years, largely because of the Mormon Church, the state has been a magnet for people who mostly stayed put. A relatively small founding population was fruitful and multiplied--aided in the 19th century by polygamy, which allowed husbands to have more than one wife. With its emphasis on family records and genealogy, the Mormon church then created a treasure trove of details about those people.

DNA RESEARCH

The rest was left to science. In the 1970s, scientists began melding church records with every measure of public health and mortality they could find, creating a vast database that researchers can use to cross-index family trees with disease patterns and death rates.

In the 1980s, a study of the genetic makeup of 50 big Mormon families, containing more than 650 people, was begun. The families have repeatedly been revisited for study.

"We know probably more about the definitions of the DNA segments in those individuals than in any others, anywhere," says Jean Weissenbach, the director of the French National Sequencing Center, which used samples from the Utah families in its work on the Human Genome Project, a multinational effort to define and delineate DNA, which was completed in 2003. (DNA consists of helix-shaped molecules that contain the building blocks of life.)

THE POWER OF NUMBERS

People like Norm Jones help explain how Utah is different. A missionary who serves at the Mormon Church's Family History Library, Jones, 69, traces his roots to the 1840s in Salt Lake City, about the time Mormon leader Brigham Young led his followers to land that became the state of Utah, from Illinois and other points east. Jones says he often wanders up to help a library patron and finds that they have a common ancestor. "After a while, you're related to everybody," he says.

What Utah offers, researchers say, is partly the power of numbers. The life and health histories of 1.6 million Utahans, living and dead, have been incorporated into the Utah Population Database at the University of Utah.

Polygamy, though now illegal, also left Utah with an advantage as a DNA laboratory: Because thousands of families are descended from polygamists, the genes of a relatively small group of men have been amplified in the biological record, allowing researchers to follow their trail through offspring with different women.

The Utah research is helping lead a revolution in genealogy. The Sorenson Molecular Genealogy Foundation is compiling what it hopes will be the world's largest global genetic database to assist Utahans and others in finding their roots. The foundation's chief scientist, Scott R. Woodward, says the goal is to have DNA samples of 100,000 people within a few years, focused primarily on Western European ancestry. About 40,000 samples are already available, he says.

When the database is completed, a person should be able to walk into the office, provide a DNA sample with a quick swab of the cheek, and get a report back saying what place--perhaps down to the town or county--that person's genes are most likely from. "Genealogy was the starting place," Woodward says. "Genetics has now made the tools to go back and verify the genealogy."

Kirk Johnson is Denver bureau chief for The New York Times.