Demystifying DNA Results
What happens after you order a DNA test? What does that pile of numbers mean? Our layperson's guide addresses privacy concerns and tells how to analyze your results report.
Testing anxiety
Happily, DNA testing no longer involves bloodletting. You’ll order a test and get a cheek-swab kit—a toothbrush-like device you use to painlessly scrape the inside of your cheek—in the mail. You ship your cells to the testing company, which codes the sample to protect your identity and sends it to a university lab for testing.

With “Big Brother” privacy concerns getting so much attention these days, DNA testing may seem risky. What if the wrong people get their hands on your results—could they find out whether you’re a health time bomb waiting to explode? Learn your true parentage? Keep your sample and use it again without telling you? It’s highly unlikely: The testing that’s done for genealogical purposes differs from medical, paternity or criminal testing. In fact, if police were to use Y-DNA testing to solve a crime, they’d have to haul in hundreds or thousands of distant cousins as suspects.

Testing companies promise to keep your identity and test results secure. If you choose to have your results posted in an online database, you’ll be identified by code rather than by name. The Web site can serve as an intermediary should a match want to contact you—or you can withhold your contact information. Surname-project managers who receive results for their group generally post results on the Web using a code or, as is rapidly becoming the standard, the name of the earliest known ancestor. If you’re concerned, you can deny the testing company or project manager permission to share your data in any way.

Ask your testing company what happens to samples after they’re tested. Some companies destroy them; others keep them (unless you direct otherwise) in secure storage in case a client wants additional, more-precise tests. Since the lab knows you’re interested in genetic genealogy, you may be asked to participate in research studies, but no reputable lab will test your sample without your permission.

Getting results
You’ll probably wait two to six weeks to receive your results in the mail or online, if you used a company that lets you view your results on its Web site using an access code. They’ll consist of a chart with what resembles a pile of numbers. If you took the popular Y-DNA test, they represent the numbers of STRs for each marker your test evaluated. How do you interpret them? You’ll want to perform three levels of analysis:

1. Within your surname project: If you’ve joined a DNA surname project, your first step is to compare your results with others in your project. A person with a perfectly matching haplotype will show the same number of STRs for each marker as you; a near match will show differences (or mutations) on perhaps one to three markers—the rarer your haplotype, the more mutations you’re willing to tolerate in a match. It’s definitely worth collaborating on genealogical research with matches and near matches. Your family trees likely overlap at some point, so share details about your earliest known ancestor and where he resided—even if your MRCA predates a paper trail. Maybe you know your ancestor hails from Ireland, and a few of your matches have traced their lines to County Armagh. Now you know where to focus.

If you’re a genetic orphan in your study—with no haplotype matches in sight—you’ll just have to wait. As the project grows, someone should eventually match you. If you have no matches in a sizeable project, it’s probably time to inspect your research for errors and hints of illegitimacy, adoptions or other nonpaternity events.

2. Through your testing company: Whether or not you have any matches within your study, look at the information your testing company supplies. For instance, most companies provide a list of customers outside your project who share your haplotype or come close (and have given the company permission to share their information). If you have a common haplotype that's shared by 50 others, you probably won't want to launch an e-mail campaign — but if you match only one or two others, it doesn't hurt to contact them.

Your testing company may provide other information, such as an ethnic analysis that lists the self-declared nationalities or ethnicities of your close matches. A customized analysis might blend and interpret your genealogical and genetic data, even indicating when a mutation might have occurred or where your research may have a glitch.