This is Part 1 of a series about mitochondrial DNA, abbreviated as mtDNA, and how to use it successfully for genealogy.
What is Mitochondrial DNA and Why Do I Care?
Mitochondrial DNA is different from nuclear, or autosomal, DNA. Nuclear DNA resides within the nucleus of a cell, while mitochondrial DNA resides outside the nucleus.
Every cell has thousands of mitochondria while it only has one nucleus.
Mitochondrial DNA is a circular ring with 16,569 base pair locations. The biological purpose of mitochondria is to power the organism, converting chemical energy into a form that the cells can utilize.
Mitochondrial DNA is also different from autosomal DNA in how it is passed to offspring.
Mitochondrial DNA is unique because all people, males and females, inherit their mitochondrial DNA from their mothers, but only females pass it on to their children.
The chart above illustrates which individuals in your tree inherit their mitochondrial DNA from whom.
The daughter and son both inherit their mitochondrial DNA from their mother, who inherits hers from her mother, and so forth – on up the direct matrilineal line. You can read about the difference between matrilineal and maternal lines, here. In essence, maternal can be referring to anyone on your mother’s side of your tree, while matrilineal is your mother’s mother’s mother’s line ad infinitum.
However, every person in this tree carries mitochondrial DNA of specific ancestors.
The red arrows show the inheritance path of mitochondrial DNA for individuals whose contributors are also in the tree.
The father of the children inherited his mitochondrial DNA from his magenta mother’s matrilineal line.
His father inherited his mitochondrial DNA from his lavender mother’s line.
The maternal grandfather in dark blue inherited his mitochondrial DNA from his red mother’s line.
The gold arrows show that the contributors of these individuals are not shown on this tree, but they all inherited their mitochondrial DNA from their matrilineal lines as well.
When discussing mitochondrial DNA, we generally think in terms of ourselves, but the application of mitochondrial DNA to genealogy is as far reaching as all of our ancestors.
Each line has its own unique story for us to harvest – assuming we can find an appropriate candidate for testing or find someone who has already tested.
Why Mitochondrial DNA Works
Mitochondrial DNA is inherited from our matrilineal line directly, with no genetic contribution from any males. This inheritance path allows us to use mitochondrial DNA for matching to others reaching back generations as well as providing a way to view beyond the line-in-the-sand of surnames.
In other words, because mitochondrial DNA is not mixed with DNA from the fathers, it’s very nearly identical to our matrilineal ancestors’ mitochondrial DNA many generations ago.
In fact, by tracing a series of mutations, we can track our ancestor over time from mitochondrial Eve, born in Africa tens of thousands of years ago to where we are today.
If mutations never occurred, the mitochondrial DNA of all people would be identical and therefore not useful for us to use for genealogy or to peer back in time beyond the advent of surnames.
Mutations do occur, just not on any schedule. This means that it’s difficult to predict how long ago we shared a common ancestor with someone else based solely on mitochondrial DNA mutations.
There might be a mutation between us and our mother, or there might be no mutations for hundreds or even, potentially, thousands of years.
Part of the success of matching genealogically with mitochondrial DNA testing has to do with the regions tested.
Testing fewer locations results in matches that are much less relevant.
Mitochondrial DNA is divided into 4 regions used for genealogy.
- HVR1 – Hypervariable Region 1 – locations 16021-16569 (548 total locations)
- HVR2 – Hypervariable Region 2 – locations 1-437 (437 locations)
- HVR3 – Hypervariable Region 3 – locations 438-576 (138 locations)
- Coding Region – the balance of the mitochondria (15,445 locations)
If you think of mitochondrial DNA as a clock face, the hypervariable regions span the time from approximately 11-1. The Coding Region is the balance.
Matching at the HVR1 or HVR1 plus HVR2/3 levels alone can reach back thousands of years in time. I strongly encourage testers to test at the higher full sequence level with the mtFull product, allowing much more granular matching.
The HVR1, 2 and 3 regions are exactly as their name suggests – hypervariable – meaning that they mutate faster than the coding region.
The mtFull or full sequence test tests the entire mitochondria – all 16,569 locations.
Genealogists need a full sequence test in order to do two things:
- Match with other testers reliably
- Obtain a full haplogroup which acts as a periscope in time, allowing us to look much further back in time than autosomal and on one specific line. There’s no confusion as to which line the results came from with mitochondrial DNA.
The coding region carries most of the potentially medically relevant locations. Medical data is not provided in the results of the testing – only genealogically relevant information.
Family Tree DNA does provide for HVR1 and HVR2/3 results to be shown in projects that testers join, if testers so choose. Coding region results are never shared anyplace unless individual testers share them individually with each other.
I’m personally not concerned about this, but mitochondrial DNA testing has been occurring for 20+ years now and it was uncertain at that early date what medical information might be discovered in the coding region, so the decision to not share was made by Family Tree DNA at that time and remains in effect today.
So, what can people see of your actual results?
What Matches See
People whom you match can see that you do match, but they can’t see any differences or mutations. They see the name you’ve entered, your earliest known ancestor and can send e-mail to you. Aside from that, they can’t see your results or mutations unless you’ve joined a project.
Within projects, participant names are never listed publicly. In other words, your matches can’t tell that it’s you unless they recognize your earliest known ancestor on the project list and you are the only person with that ancestor.
Don’t worry though, because only your HVR1 and HVR2 region results are listed in projects, as shown in the next section.
Benefits of Joining Projects
The great news is that even if you’ve just ordered your test and are waiting for results, you can research and join projects now.
Projects at Family Tree DNA provide testers with access to volunteer administrators to help as well as clustering users in projects that are meaningful to their research.
The haplogroup A project is shown above with maternal earliest known ancestor (EKA) names as provided by testers.
Another important project feature is the project map function, allowing testers in a specific haplogroup to view the locations of the earliest known ancestors of other members of the same haplogroup – whether they match each other or not. Your ancestors traveled with theirs and descended from a common ancestor. Cool, huh!
For example, here’s the haplogroup A10 cluster around Montreal. What’s the story associated with that distribution? Whatever it is, it’s probably important genealogically.
Here’s haplogroup A5a1a1 in Japan.
Do you have clusters? You can see if you join relevant projects.
Another type of project to join is a geographical or interest group.
The Acadian AmerIndian Project welcomes descendants who have tested the Y, autosomal and/or mitochondrial DNA of the various Acadian families which includes French and English settlers along with First Nations indigenous ancestors.
The map shows the distribution of the haplogroup A2f1a ancestors of various Acadian testers.
Projects such as the Acadian AmerIndian Project facilitate genealogists discovering the haplogroup and information about their direct line ancestor without testing.
For example, if Anne Marie Rimbault, shown above, is my ancestor, by viewing and hopefully joining this project, I can harvest this information about my ancestor. I can’t personally test for her mitochondrial DNA myself, but thankfully, others who do descend matrilineally from Anne Marie have been generous enough to test and share.
Furthermore, I’ve contacted the tester through the project and gained a great cousin with LOTS of information.
Just think how useful mitochondrial DNA would be to genealogists if everyone tested!
Finding Projects to Join
I encourage all testers to join appropriate haplogroup projects. There may be more than one. For mitochondrial haplogroup J, there is only one project, but for those who carry haplogroup H, there is a haplogroup H project and many additional subgroup projects.
I also encourage you to browse the selections and join other interest projects. For example, there are projects such as Cumberland Gap which is regional, the American Indian project for people researching Native ancestry, in addition to your relevant haplogroup project(s).
When deciding which projects to join, don’t neglect your mitochondrial DNA. Your selection may be a huge benefit to someone else as well as to your own research.
How to Join Projects
Next, you’ll see a list of projects in which your surname appears. These may or may not be relevant for you.
You can search by surname.
More importantly, you can browse in any number of sections.
For mitochondrial DNA, I would suggest specifically mtDNA haplogroups, of course, along with mtDNA Geographical Projects, Dual Geographical Projects, and mtDNA lineage projects.
Surname projects are more challenging for mitochondrial DNA since the surname changes every generation.
When you find a project of interest, click to read the description written by the volunteer administrators to see if it’s a good fit for you, then click through to join.
Next Article in the Series
Of course, you’re probably wondering what all of those numbers in your results and shown in projects mean. The next article in about a week will address exactly that question.
These articles may be of interest.
Mitochondrial DNA is often confused with X DNA, and they are not at all the same.
Mitochondrial DNA can quickly confirm or put to rest that Native American ancestor family story.
A great example of using mitochondrial DNA to break through a brick wall that would never have fallen otherwise!
If you haven’t yet tested, your can order your mtFull Sequence test today!
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