12 Gene Tests That Could Change Your Life

A massive worldwide hunt for disease-causing genes is starting to yield results. Seven years after the genome project, powerful new gene chips that can scan up to one million locations across your DNA are beginning to pinpoint genes that are at the root of killers from breast cancer to heart disease to diabetes.

Not too many years from now, researchers predict that gene findings will be used to create genetic report cards that could help predict one's risks for cancer, heart disease, diabetes, schizophrenia and more. Biotech companies are hopeful that the gene screens will form a new multibillion-dollar business, promising a new kind of preemptive care. But skeptics wonder whether premature genetic testing could just lead to a mountain of confusing, scary or uninterpretable genetic information.

To make sense of this deluge of DNA findings, here's a quick rundown of how genes work. Each gene is a recipe written in DNA for a molecule that does a job in the body; each of us gets one copy from mom and one from dad. For some diseases, only a single bad copy can cause a disease; for others, you need two bad versions. What researchers are finding when they find a "bad gene" is a problematic version that can cause disease. These problem genes are being found at an amazingly rapid rate.
By The Numbers: 12 Gene Tests That Could Change Your Life

In the past three months scientists have unearthed solid evidence for six diabetes-causing gene variants, several variants involved in prostate cancer and an obesity gene that adds 7 pounds of fat if you have the bad version. Two groups have found a genetic quirk on chromosome 9 that boosts your risk of having a heart attack by 40% to 60%. In late May British researchers using a study of 44,000 patients published data pointing to four new genes linked to breast cancer.

Francis Collins, who heads the gene-hunting effort at the National Institutes of Health, predicts "an avalanche" of new disease-gene findings in the next year. "Every geneticist is doing this right now. It is a gold rush," says Dietrich Stephan at Translational Genomics Research Institute, a Phoenix nonprofit that recently pinpointed genes that affect human memory.

In the long run, researchers hope the gene findings will lead to potent new treatments. But that will take a while. New gene tests will come sooner. DeCode Genetics just began selling one gene test aimed at forecasting diabetes risk and plans another test for heart-attack risk. Celera sells a gene test to predict whether your liver is vulnerable to the hepatitis C virus, to help determine whether toxic drugs are necessary (many infected people never get symptoms). And Roche sells a chip that analyzes genes in the liver to determine whether it can properly digest various drugs. It remains to be seen whether these tests will catch on, but one gene test is already a commercial hit: Myriad Genetics (nasdaq: MYGN - news - people ) sells test for the breast cancer genes known as BRCA1 and BRCA2. Its gene test sales are at $100 million a year and growing at a 40% clip.

"There has been a demystification of genetic testing," says Washington University's Timothy Pluard. "To some degree genetic testing is not very different from having your cholesterol levels" measured. Already, various gene tests are available via the Web from DNA Direct and others. And Anne Wojcicki, wife of Google (nasdaq: GOOG - news - people ) founder Sergey Brin, has started a company called 23andMe to help people interpret their personal genetic information.

It is likely that many genes will prove to be involved in raising the risk of developing a particular disease. Genes for certain rare inherited ills such as Huntington's disease guarantee you will get sick, but many of the new genes being discovered for diabetes and other common diseases tweak your risk by only 20% to 30%--not enough to make you change your life. Researchers may have to isolate dozens of such genes and assess their effects before they gain a clear picture of future risk.

Once the genes are identified, it could take years before doctors figure out what to about it. The breast cancer genes BRCA1 and BRCA2 were spotted in 1994 and 1995, but the tests weren't used much initially because "it wasn't at all clear we could do anything," says Noah Kauff, a cancer geneticist at Memorial Sloan-Kettering Cancer Center. But now women have options, including the removal of the ovaries or breasts, better MRI scans that can spot breast tumors early and a preventative drug tamoxifen that works for those with BRCA2. Studies have shown that removing the ovaries alone--a more palatable intervention to some than a double mastectomy--can also reduce breast cancer risk by 40% to 70% in those with the gene mutations.

Deborah Schmidt, 40, got the test after her mother developed both breast and ovarian cancer. She was stunned to find out that she had the bad BRCA2 mutation too. "I stared at the paper for a long time," she recalls. But she does not want to have her breasts and ovaries removes, as some women do. A fit single mother of a 9-year-old boy, she hopes to find a husband and have another child first. "I'm giving it until 45" before reconsidering the surgery, she says. Her choice is to get "nerve wracking" mammograms and breast MRI scans twice a year. As more and more genes that boost disease risk are found, many people could face similar choices.