DNA Testing for Genealogy – Getting Started, Part Two
We’re excited to bring to you part 2 of YourGeneticGenealogist.com blogger CeCe Moore’s DNA Testing for Genealogy series. For the next few weeks, she’ll be providing a great overview about DNA testing for genealogy. Enjoy!
Last week we discussed the Y-DNA test that only traces your direct paternal line back in time, but there’s good news for you women who felt left out. Did you know that there is also a DNA test that traces your direct maternal line back in time? It is called a mitochondrial DNA (mtDNA) test.
Illustrating the path of Y-DNA in blue and mtDNA in red (credit: Angela Cone)
Mothers pass mtDNA to their children, both sons and daughters, but only females pass it on. Your mtDNA was inherited from your mother and from her mother and from her mother. No matter how far back in time you go, you only have one direct maternal ancestor in each generation and she is the one responsible for passing you your mtDNA. Your mtDNA has followed this matrilineal path down through the generations for many thousands of years intact and virtually unchanged.
Mitochondrial DNA testing is a great tool for discovering more about the females in your family tree. As all dedicated genealogists have undoubtedly experienced, female ancestors are frustratingly difficult to trace because of the fact that they traditionally change their surname with marriage. So, for many of us, anything that may shed light on our female ancestors’ origins is welcome. The value of mtDNA testing is in the simple fact that if two people share an exact mtDNA sequence, then those two people descend from a common female ancestor somewhere in the past. For each individual, your mtDNA will only reflect that of your direct maternal line, however following the same rule applied to Y-DNA, any female ancestor of interest can be followed down the tree to the present day in an attempt to find an appropriate direct maternal descendant for mtDNA testing. For example, my third great grandmother Sarah’s origins are unknown. In order to gain more insight into her ancestry, I ordered a mtDNA test for my mother’s first cousin who is matrilineally descended from Sarah.
Without getting bogged down in technical details, there are two important aspects of mtDNA results for the genealogist just venturing into genetic genealogy. The first is the match list.
Upon completion of your test, you will receive a list of matches. Only exact mtDNA matches are relevant for genealogical purposes and the higher the resolution of the test, the better. (I suggest testing at least HVR1 and HVR2, called “mtDNA Plus” at Family Tree DNA.) The surnames on your list will likely all be different since they are not retained through female lines. The goal is to determine your shared ancestor with these matches. However, because mtDNA changes (mutates) very slowly and can be passed down virtually unchanged for thousands of years, your mtDNA may be identical to that of your very distant direct maternal ancestors. For this reason, it is often impossible to find the genealogical link to your matches. For example, I have an exact mtDNA match with whom I have compared direct maternal pedigrees back to the 1500’s without finding our common ancestor.
One unexpected side benefit of mtDNA testing for me is the personal connection that I have gained to my direct maternal ancestors’ homeland. In an attempt to discover our shared roots, my Finnish match mentioned above generously extended my direct maternal line back for many generations using the local parish records in Finland. These records are not online and I might not have ever had the opportunity to examine them in person. Although we never did find our shared ancestor, we have enjoyed a wonderful friendship and I feel a much more personal connection to my Finnish roots.
Mitochondrial DNA can offer us a fascinating glimpse into the ancient origins and migratory patterns of our ancestors. When you take a mtDNA test, the testing company will not only give you a match list, they will identify your haplogroup. Simply put, your haplogroup will be a letter assignment that groups you with those with whom you share the most similar mtDNA. Since certain haplogroups originated in specific geographic regions, it is sometimes possible to extrapolate valuable information from these assignments that is genealogically relevant. For example, my haplogroup subclade appears to be found exclusively in those who matrilineally descend from Finnish women. In my case, I already had knowledge of my Finnish direct maternal line, but one of my matches was brick walled in Colonial America in the early 1700’s, so this was very illuminating for her family.
Geographic origins and migration patterns of mtDNA haplogroups
If you decide to take a mtDNA test for genealogy, let me suggest that you go into it with patience and tempered expectations. Identifying a common ancestor with your matches may prove to be impossible since your connection may be before genealogical time. Additionally, even though mtDNA mutates slowly, your individual signature may still be quite unique. Therefore it is not unusual to have zero exact matches in the database simply because only a small percentage of the population has tested thus far. Time will, undoubtedly, bring more matches as increasing numbers of people become interested in testing.
Although much can be learned from our mitochondrial DNA and my own mtDNA testing experiences have been very positive, it is not my first choice for the female genealogist wanting to take her first DNA test. Join me next week for a discussion on my personal favorite type of DNA testing for genealogy – autosomal DNA.
(Update: Read part 3 here).
CeCe Moore is a professional genetic genealogist and writes the popular blog Your Genetic Genealogist. She is the Southern California Regional Coordinator for the International Society of Genetic Genealogy and the administrator of the organization’s DNA Newbie Yahoo Group. CeCe serves as an “Ancestry Ambassador” to 23andMe and on the advisory board of the Mixed Roots Foundation and is a member of Mensa. Her favorite genetic experiment is her seven-year old son, Nicolas.