To really be able to digest the information you’re going to get in your DNA test, you have to understand a few key things about DNA itself, aside from just that famous image of the double helix, with each rung making a “base pair.” One single gene can have anything from 27,000 to 2 million base pairs, and there are over 3 billion base pairs across the 23 chromosome pairs in the nucleus of each cell in the human body. All of which is to say, DNA is extremely complex. Don’t worry though, you don’t have to be a nuclear physicist to get the basics.
First off. The human genome is 99.9 percent identical in every person on the planet, but that 0.1 percent contains all of the things that make you, well, you. It follows that DNA testing companies will concentrate on that 0.1 percent to determine their conclusions, right? Well, not exactly. Scientists have been able to identify proteins that are linked to conditions, diseases, or health risks—and direct-to-consumer DNA testing companies have developed algorithms based on studied mutations, variations, and changes in genetic makeup. So, no DNA testing company is going to analyze your whole genetic code, but rather certain markers, usually related either to ancestry or to health.
But I’m definitely related to Anastasia Romanov, right?
Companies that offer DNA ancestry tests usually offer several types:
- Autosomal, focusing on autosomes 1 through 22, and the X chromosome. These are based on a mix of both your parents’ DNA, and theirs, and so on and so forth— so just the past 200 years could represent 510 people. But these tests compare alleles against contemporary populations that have remained living in one place for a long time, so it doesn’t really take into account all the genetic mixing that happens naturally in any given area.
- Y-DNA tests, which are based on the Y chromosome, or your ancestor’s on your dad’s side. While this type of test is considered more reliable in the scientific community, they can only trace one patrilineal ancestor on your dad’s side, because in each generation, you’re only seeing one bloodline. That means that it’s really hard to determine accuracy as you move up the family tree, since this test won’t include any female ancestors.
- mtDNA tests, that test mitochondrial DNA, or your mom’s side of the family. This test has the same sort of limitations as the Y-DNA tests, for the identical reason that it only traces the female ancestors on your mother’s side of the family.
As you can see, each test has its own limitations. And none of them can tell you whether you really are the great-great-great-descendant of Grand Duchess Anastasia Nikolaevna of Russia.
How do I know if my ancestry test is accurate, then?
Well, as we mentioned above, it really depends on what you’re looking for—and some tests are more accurate than others, or at least they paint a wider picture. It also depends on the size of the company’s database, since that’s what they’ll be comparing your DNA to. This is especially limiting for people of color, since they are quite often underrepresented in these databases. Look for a company that is transparent about the contents of their databases, then, to ensure greater accuracy. Finally, you should also be aware that false-positives do happen, though they’re rare. Typically, DNA kits are not covered by health insurance but knowing your family’s DNA history is never a bad idea for people to consider.
Author: Sam Klau