Consumer genetic testing is expanding as more than 26 million people have taken this kind of test, according to the MIT Technology Review.

Even a 99.9 percent accuracy can result in discrepancies because, with 1 million genome places, there is a chance of 1000 errors.

DNA tests are still considered estimates, due to imperfect data.

In genetic ancestry testing, even identical twins who have virtually the same DNA may or may not get the same results.