Mehmet and Mike are happily married. No, not to each other. To two wonderful ladies (one each, of course). But if they weren't and they lived, say, near Boston, a peculiar dating service might arouse their curiosity. For $1,995.95, a company called ScientificMatch.com claims that if you crack open its special kit, rub a cotton swab on the insides of your cheeks and ship the swab to its lab, it will use the DNA it collects to find your soul mate.

The company examines the genes that relate to your immune system - technically, the genes in your major histocompatibility complex (MHC) - to match you with another member of the dating service who has a very different MHC makeup. Studies suggest that people are more likely to feel that romantic lightning-in-a-bottle called "chemistry" when they have genetically dissimilar immune systems. (One theory suggests that blending diverse genes gives children stronger immune systems, so it's an advantage.)

This matchmaking venture is just one of dozens of consumer-based genetic testing services that have popped up in recent years. Many others promise to look into your DNA and tell you whether you're susceptible to certain medical disorders. For about $1,000 and up (not covered by health insurance), services such as 23andMe, Navigenics, Genelex, deCODE Genetics and others will scan your DNA for gene markers linked to heart disease, Alzheimer's, multiple sclerosis, diabetes, certain cancers and more.

Beyond these pricier services, many over-the-counter DNA test kits are now sold in drugstores for as little as $30. Send in your swab and, for an additional $200 and up, they'll test your DNA for markers of lupus, depression, glaucoma, celiac disease ... the list goes on.

Are they legit? In the case of romantic bliss, we have seen the studies linking diverse MHC with sexual attraction in animals and humans. But we also know that these limited studies - like nearly all research involving genetic testing - probably reveal only a tiny part of a complex process that nobody truly understands yet. So we'd take advice from ScientificMatch.com (or any other personal DNA-mapping service) with a grain of salt.

Gene testing is an amazing tool. Mapping the human genome has yielded powerful new weapons against cancers of the breast, ovaries, colon, prostate and others. In fact, we have colleagues who refer people for testing for the BRCA 1 and 2 breast-cancer genes every week. For adopted children, gene testing may be the only way to acquire valuable medical information. These tests are conducted by certified laboratories and interpreted by physicians who can help patients decipher and use the findings.

Also, while research has identified genes that contribute to about 1,400 diseases or disorders, so far most of these provide only preliminary clues. And with certain diseases, such as Alzheimer's, genetic mutations don't always mean you'll get a disease.

The Food and Drug Administration doesn't regulate the quality of the counseling you get after using one of these consumer DNA tests. These kits could give you helpful information, or leave you feeling falsely safe or scared. Before trying one, start with these tips:

Thoroughly discuss your family medical history with your doctor, going back to your grandparents. This can yield vital information.

If you decide to go ahead, be sure that the company keeps your test results confidential.

Review the test results with your doctor or a certified genetic counselor (ask your doc for a referral), not just a rep from the testing company, especially before buying pricey supplements or additional services.

The You Docs - Mike Roizen and Mehmet Oz - are authors of the best-selling "You: The Owner's Manual" and "You: On a Diet." To submit questions and for more info, go to www.RealAge.com.