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Understanding your mtDNA results

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Written by Kimberli Faulkner Hull
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© Kimberli Faulkner Hull

mtDNA, or mitochondrial DNA, comes from your matrilineal ancestors. If you have your tree/pedigree chart set horizontal, so you are on the far left, the matrilineal line is on the bottom: Your mother, her mother, her mother, her mother, etc. While your brothers and sisters also inherited mtDNA from your mother, your brothers can’t pass it down, so it stops with them. Only you and your sisters will pass down your mother’s mtDNA.1

Understanding your mtDNA results
Matrilineal ancestors

mtDNA haplogroups

Let’s start with your haplogroup and the first letter it begins with – let’s use H as an example. Imagine thousands of years ago that a woman named Helena leaned against the trunk of a tree with a big “H” carved into it and her six sisters chose six different trees with different letters to lean on. She liked it there and stayed, so H was her location. By the way, I didn’t come up with the name Helena. Bryan Sykes wrote a book back in 2001 based on the concept of mtDNA called the Seven Daughters of Eve and he christened each of the six maternal line founders of the known mtDNA haplogroups with a name and he gave “H” the name Helena.2

The Seven Daughters of Eve, Bryan Sykes, 2001.
The Seven Daughters of Eve, Bryan Sykes, 2001.

Now, imagine Helena had children, and her daughters had children, and so on. The sons all went to live with their fathers, but the daughters and their daughters all stayed at H. These particular types of trees grow really slow but, at one point down the line, the tree grew large enough that one of the female descendants had a daughter and decided put the baby girl up on the seventh branch of the tree to live. The daughter’s address was H7 and when she had daughters, they all lived at H7 too.

That is like the H7 of my haplogroup, H7d1. It is just an address on a sub-branch of the “H” tree. The ancient ancestor was H and, at some point, something changed in the mtDNA and the resulting sub-branch was called H7. mtDNA does not change or mutate very often, so generations remain constant for a very long time.3

The final piece of the puzzle is the rest of the haplogroup – for me that is the d1 of H7d1. Each mitochondria has 16,569 bases or locations that, in a full sequence test, are each tested and then compared to a reference value. In the testing, they are looking for differences – there are far, far more similarities. What do they test for? Nucleotides, which are adenine, cytosine, guanine, and thymine. You can just think of them as A, C, G and T. In my example, the required mutations for H7d1 are C2283T and A13032G.4

What does this ! mean?

Do you happen to have an exclamation point in your haplogroup? It means somebody from your haplogroup went out on a new branch and the family stayed there awhile, then someone decided to go back to the original branch. It is called a back mutation and simply means there was a change or mutation in the mtDNA that changed back or reverted to the ancestral or original state at some point – kind of like a U-turn The exclamation point designates the place where the back mutation occurred.5

mtDNA matches

mtDNA matches, names removed for privacy

Now, let’s talk about mtDNA matches. The first column on the mtDNA Matches page is genetic distance. Genetic distance, some people call it steps, is how many differences two people have when you compare their results.6 While all the people in your list of matches have the same haplogroup as you, if the genetic distance is zero, they are an exact match to you. “FMS” on their line means they took the full sequence test as well and, when compared to the references used by FamilyTree DNA to evaluate and compare mtDNA test results, they had results that were identical to your results.7

As noted above, mtDNA mutates very slowly and can reach thousands of years back, so a genetic distance of even a two typically means the common ancestor may be too far back to be of use.8


Endnotes

1. Blaine T. Bettinger and Debbie Parker Wayne, “Genealogical Applications for mt-DNA,” Genetic Genealogy in Practice (Arlington, VA: National Genealogical Society, 2016), pages 45-60, particularly page 45-47.

2. Bryan Sykes. Seven Daughters of Eve (W.W. Norton & Company Inc, 2001), page 40 and “K mtDNA Haplogroup, About us” FamilyTree DNA, (https://www.familytreedna.com/groups/mt-dna-k/about/background : accessed 12 June 2019).

3. Blaine T. Bettinger and Debbie Parker Wayne, “Genealogical Applications for mt-DNA,” Genetic Genealogy in Practice (Arlington, VA: National Genealogical Society, 2016), pages 45-60, particularly pages 52-54.

4. Elise Friedman, “Advanced Topics at FamilyTree DNA, Part 2: mtDNA,” video, uploaded 21 Mar 2015; YouTube: FamilyTree DNA Channel, 1:24:50, (https://www.youtube.com/watch?v=0bMjr7kVFL8&feature=youtu.be : accessed 10 June 2019).

Also. “mtDNA Haplogroup Mutations,” FamilyTree DNA (https://www.familytreedna.com/mtdna-haplogroup-mutations.aspx : accessed 22 Jan 2022), haplogroup H7d1, required mutatoins C2283T and A13032G.

5. Roberta Estes, “Mitochondrial DNA: Part 2 – What Do Those Numbers Mean?” DNAeXplained – Genetic Genealogy, (https://dna-explained.com/2019/05/23/mitochondrial-dna-part-2-what-do-those-numbers-mean/ : accessed 10 June 2019).

6. Genetic distance,” International Society of Genetic Genealogy Wiki (https://isogg.org/wiki/Genetic_distance: accessed 11 June 2019).

7. “Full Mitochondrial Sequence (FMS),” FamilyTree DNA, FamilyTree DNA Learning Center (https://www.familytreedna.com/learn/faq-items/full-mitochondrial-sequence-fms/ : accessed 10 June 2019) and “mtDNA – Matches Page,” FamilyTree DNA, FamilyTree DNA Learning Center (https://www.familytreedna.com/learn/user-guide/mtdna-myftdna/mt-matches-page/ : accessed 10 June 2019).

8. “How do I tell how closely I am related to a mitochondrial DNA (mtDNA) match?” FamilyTree DNA, FamilyTree DNA Learning Center (https://www.familytreedna.com/learn/mtdna-testing/tell-closeness-relationship/ : accessed 10 June 2019).


Citing this page: Kimberli Faulkner Hull, author, “Understanding your mtDNA results,” Cool Adventures ( https://cooladventures.com/genealogy/understanding-mtdna/: posted 2022).

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