It's long been known that DNA evidence can be critical in cracking unsolved crimes of the past, and it's now being used to answer questions about our future.
Linda Avey is a founding partner at 23andme, an individualized genetic testing startup in the San Francisco Bay Area. Named after the 23 pairs of chromosomes in the human body, the company charges $1,000 to analyze a person's DNA, and then potentially life-altering information is delivered via the Internet.
Watch the story tonight on "Nightline" at 11:35 p.m ET
I signed up for DNA testing with 23andme, which begins with a deposit of a bit of saliva in a vial — actually, much more than just a bit.
"You have to do a lot of spitting, don't you?" I asked.
"You do," Avey said. "The study that we do is pretty comprehensive, and we need a fair amount of DNA to do that."
This process has led to a fast-growing business opportunity. 23andme has a list of diseases that it says it can test for, ranging from Type II diabetes to breast cancer.
This is a glimpse into the future of personalized medicine. There's no doctor — just you, your saliva, and an Internet connection.
"The possibility of people learning deeply unsettling things and only having a computer screen to talk to, worries me," said Hank Greely, a Stanford law professor who specializes in the societal effects of genetic research.
Avey acknowledged that having access to this kind of information isn't necessarily 100 percent positive. But she contends the pluses far outweigh the minuses.
"This is simply information that people have access to that they didn't before. And we want to give people that option," she said.
Greg Brandeau, an executive at Pixar, the animation company owned by Disney, also a parent company of ABC News, was one of the first to take that option. Initially he had a novel reason for submitting his entire family for DNA testing.
"My wife is Chinese-American. And our kids are a mixture of us, so what does that mean for them? So that was one thing," Brandeau said. "And the other was … are there things I need to worry about or things that I can plan for? And I figured if I took this test I would find out both of those things."
He found out that he is less likely to have a heart attack, be obese or develop deep vein thrombosis, but he is at a slightly elevated risk for type II diabetes. Brandeau's results didn't yield anything disturbing — but he says if he had found out that, for example, his daughter had a predisposition for breast cancer, he would tell her.
Getting the information from a computer screen, rather than a person, was not a deterrent for Brandeau.
"I guess each person should make their own choices about that," he said. "Again, I come at it from the point of view that having information is useful. I don't feel like I need a doctor sitting there telling me what it means."
When the news is bad the effects can be very different. Dr. David Witt has been conducting genetic testing and counseling for more than two decades.