Genetic Ancestry: Intro to Personal DNA Tests

Posted February 16, 2011 by Geni | One Comment


Our DNA holds the answers to a lot of questions. Ancestry is one of them. When we have our genome analyzed, we can compare our data to the community aggregate as well as known-relations. DNA testing provides us the ability to see who we’re related to, and how closely.

Family Tree DNA and 23andMe are two of the most well-known direct-to-consumer DNA testing companies. They both offer Y-DNA, Mitochondrial DNA, and Autosomal DNA tests. Family Tree DNA offers a wider range of tests with granular control, but 23andMe has a comparatively less expensive comprehensive package. The exact way that the two companies work with genetics is slightly different, but there shouldn’t be much of a difference to genealogists without a background in genetics.

Very simply put, Y-DNA traces your direct paternal lineage, Mitochondrial DNA traces your direct maternal lineage, and Autosomal DNA allows you to find out how closely related you are to other people. When you’re using genetics for genealogical purposes, that’s all you really need to know to get started. Once you’ve grasped the basics, you can read more about how genetics works.

It’s also important to note that the more data you can collect genetically, the more useful it will be for your genealogical research. For example, women don’t have a Y Chromosome, so they’ll need to have their brother, father, paternal grandfather, or paternal uncle provide a DNA sample. Also, having both of your parents’ DNA analyzed could potentially help figure out which side of your family you match on with a distant relative. If it weren’t for the substantial cost for each DNA analysis, I would recommend that you have your whole family genotyped. If you’re in the position to get the kits, they make pretty unique gifts.

I have gotten myself tested, and I’ll walk you through to process and results. Keep an eye on the blog for more updates on Ancestral DNA Tests.

Image Credit: Zephyris


  • Erich Schlaikjer

    I had my DNA sequenced at FamilyTreeDNA. It is fun. But I am not sure of its value as a genealogical tool. After doing myself, I sponsored three other people who share my surname.nnOn the 12-marker level, I differ in one allele from my second cousin (same great-grandfather). I differ in the same allele from my third cousin once removed in Germany.nnOne might suppose then, that I or my father or grandfather is a mutant from some family “standard” in that allele.nnThen I tested an Australian with the same surname, who *might* be my 6th cousin. The connection involves a bit of guesswork. Anyway, he differs from me in the same allele (DYS #391) and two others. So, 3 out of 12. He differs from my German relative in 2 alleles.nnThat was tantalising, so I paid to upgrade both of them to 25 markers (I already had 37 for myself). On the additional 13 markers, my German cousin and I differ in 1, so 2/25 differences. My Australian friend differs in 7 out of the 13 new markers from both myself and my German cousin, for a total of 10/25 differences from me.nnSo, I get the feeling that the Australian gentleman and I are not related in the way we suppose, but it is a game of statistics. If I can differ in two alleles from my well-documented German cousin, how many differences is “normal” in a distant 6th cousin? I could keep paying for more upgrades, but I have lost the feeling that it would prove anything.nnMeanwhile, on the FamilytreeDNA site, there are three people with different surnames who differ from me in just 2/25 locations, the same as my German cousin. Nobody matched me at 67 markers (I wonder if my own father would). Are those people related within documented history (say 400 years)? Seems unlikely, unless there’s a lot of illegitimacy about. And so u2026 even 2/25 is not really significant, or at most just says “yes, you are both white guys from Northern Europe”.nnHaving my mitochondrial DNA done had the amusement value of telling me that my “daughter of Eve” is Jasmine, but not much else. Again, there are some matches on FamilyTreeDNA, but nothing conclusive, and all is further obscured by the changing surnames in every matrilineal generation.nnIt was all sort of worth the ride, I suppose. Maybe future advances will make it more helpful.n