A research project at the Jackson Laboratory, financed by a $15.1 million federal grant, could lead to new insights about the chief killer diseases – cancer, heart disease, diabetes and stroke – perhaps as well as Alzheimer’s disease and such “orphan” diseases as A.L.S. or Lou Gehrig’s disease.

The project grew out of a recent perception that networks of genes, rather than specific individual genes, figure in most human diseases. To detect and trace the functions of these networks, scientists at the Bar Harbor laboratory are studying 40 strains of mice that have been bred through many generations to distill various traits like size, weight, fatness or leanness, strength, color and behavior. Mice have genes and genetic networks much like humans, but they breed a lot faster.

The 40 strains were selected from the hundreds available to represent as broadly as possible the genetic world of laboratory mice.

To explain the project, Discover magazine sent a reporter and a photographer to visit the laboratory’s Phenome Room, where scientists study the mice’s phenomes, or traits of all sorts, by measuring, weighing, examining and exercising them. Their report is published in the magazine’s May issue, describing the work as an exploration of “the genetic networks that allow us to live and cause us to die.”

Kenneth Paigen, a genetic researcher and retired director of the lab, told the visitors: “The diversity across these 40 mouse strains is as great as or greater than that of the entire human population.”

His wife, Beverly Paigen, has been investigating for two years the genes that influence levels of “good” cholesterol. Although other researchers had identified many of them, she found that many new genes were involved and that dealing with parts of a network could be easier than a single gene.

The present director, Rick Woychik, explained how different genes can make proteins that switch other genes on or off and how a network can do its work even if one member gene is disabled.

The director of the project, Gary Churchill, a statistical geneticist, told them: “What we’re trying to do is change the way people think about diseases. They’re out there looking for broken genes, but the idea of broken genes just doesn’t make sense. We’re saying, ‘Hey, reality isn’t like that.'”

As the work proceeded, the team decided that 40 strains of mice were not enough. Mr. Churchill said, “If you want to go forward, you’ve got to go big.” So he and other mouse experts have launched what they call the Collaborative Cross, an international project to produce new inbred strains from lab-grown mice, each with its own unique combination of genetic patterns. The collaboration is starting with 500 strains and is aiming at 1,000 by the year 2010.

As Mr. Churchill told Discover magazine, “We spent 100 years trying to figure out what the parts are. Now we have the parts list. We can start to ask how the parts are assembled”