Combining DNA Test Types

 

Here’s a tasty DNA testing trick: combine multiple test types for better information about your family tree. This example can inspire your own genetic genealogy research.

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My family recently visited the Jelly Belly Factory in northern California. Of course at the end of the tour they funnel you into their gift shop, where we bought a big box of Jelly Bellys. Did you know how tasty it can be to combine some of your favorite flavors? (Toasted marshmallow + chocolate pudding = hot cocoa!) What a revelation!

This got me thinking about DNA, of course. Specifically, I was thinking about the power of combining multiple test types to get a better picture of your overall genealogical relationship to someone else.

If you will recall, there are three kinds of DNA tests available for genealogists: autosomal DNA, mitochondrial DNA (mtDNA), and Y chromosome DNA (YDNA). Much of the focus these days is on how to use the autosomal DNA in our family history research. I guess this is because the autosomal DNA covers both sides of your family tree, so it is seen as a catchall for our family history. While it is a very powerful tool for our research, it can also be a bit overwhelming to try to determine how you are related to someone else.   

Combining multiple DNA tests: A case study

Let’s look at an example from my own family history. My mom matched with Tom at 23andMe. Their predicted genealogical relationship, based on how much DNA they shared, was second cousins. To begin we need to understand which ancestor could be shared by people who are genetic second cousins. To figure it out, you can count backwards, like this: people who share parents are siblings, sharing grandparents makes you first cousins, while sharing great-grandparents makes you second cousins:

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So if my mom and Tom are true second cousins (meaning there aren’t any of those once-removed situations going on—but that’s a subject for another time), then we should be able to find their common ancestor among their great-grandparents. Each of us has eight great-grandparents. Because we can’t usually narrow down shared DNA to a single person, but rather to an ancestral couple, we are really just looking at four possible ancestral couple connections between my mom and Tom. My mom doesn’t have any known ancestors, as she was adopted, so we can only evaluate Tom’s line. Tom was kind enough to share his pedigree chart with us, and he had all four of his couples listed. But how do we know which one is the shared couple with my mom? 

Now, for those of you without an adoption, you will have some other clues to help you figure out which of the four (or eight, if you are looking at a third cousin, or 16 if you are looking at a fourth cousin) ancestral couples is shared between you and your match. Start by looking for shared surnames. If that comes up short, evaluate each couple by location. If you see an ancestral couple who is in a similar location to your line, then that couple becomes your most likely connecting point. What then? Do genealogy!! Find out everything you can about that couple and their descendants to see if you can connect that line to your own. 

However in my mom’s case, we didn’t have any surnames or locations to narrow down which ancestral couple was the connection point between our line and Tom’s. But even if we had locations, that may not have helped as Tom’s ancestry is very homogenous: all of his ancestors were from the same place. 

But we did have one very important clue: the mitochondrial DNA, which is partly evaluated in your 23andMe autosomal test. Remember, mtDNA traces a direct maternal line. So my mom’s mtDNA is the same as her mom’s, which is the same as her mom’s etc. 

At 23andMe they don’t test the full mitochondrial DNA sequence (FMS) like they do at Family Tree DNA. For family history purposes, you really want the FMS to help you narrow down your maternal line connection to others. But 23andMe does provide your haplogroup, or deep ancestral group. These groups are named with a letter/number combination. My mom is W1. 

We noticed that Tom is also W1. 

This meant that my mom and Tom share a direct maternal line – or put another way, Tom’s mother’s mother’s mother was the same as my mom’s mother’s mother’s mother. That means that there is only one couple out of the four possible couples that could connect my mom to Tom: his direct maternal line ancestor Marianna Huck, and her husband Michael Wetzstien. 

Now you can only perform this wondrous feat if you and your match have both tested at 23andMe, or have both taken the mtDNA test at Family Tree DNA.

Just as a Popcorn Jelly Belly plus two Blueberry Jelly Bellies makes a blueberry muffin flavor explosion in your mouth, combining your autosomal DNA test results with your mtDNA test results (or YDNA for that matter) can yield some interesting connections that just might break down that family history brick wall.

Learn more about testing your DNA with 23andMe with my quick reference guide. 23andMe offers a clean, beautiful interface on its website, but boy, there are a lot of options! This guide will tell you exactly what you need to know to navigate the 23andMe website for your family history purposes.


Originally published March 2017 on genealogygems.com.