Create a DNA Testing Plan

To solve family history mysteries with DNA, you need a good DNA testing plan. Here’s how to create one.

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Most people pursue DNA testing for family history for two main reasons: first, because they have a family history mystery they are trying to solve; or second, just because it seems like a good idea (everyone else is doing it, right?).

Whatever your reason, but ESPECIALLY if you are trying to solve a mystery, you need a plan. Otherwise you might spend way too much money on the wrong test, and way too much time analyzing results before finally discovering that test can’t tell you what you hope to learn.

Create a DNA testing plan

Creating a good DNA testing plan will maximize your chances of finding out more about the ancestor you are researching. Let’s say, for example, that you are trying to find the parents of your mom’s dad’s mom, your great-grandmother, Jane Lewis. You only carry about 12% of her DNA (you have 50% of your mom’s, 25% of your grandpa’s), and only about 6% of the DNA of the people we are trying to find (Jane’s parents).


So if we want to know more about Jane and her parents using DNA, we need more DNA. Testing any of the descendants of Jane will be helpful. However, most helpful will be your second cousins, people who are descendants of one of Jane’s other children; the descendants of your grandfather’s siblings. (You might want to read this article about getting your relatives to take DNA tests.)

The test to start with, in this case, is the autosomal test, which sheds light on both sides of a person’s family tree for about five or six generations back.

By finding and testing a second cousin, not only are you able to capture more of Jane’s DNA, but you are able to isolate the DNA you received from Jane and her husband (we can’t separate the two at this point) from the DNA you received from your other 7 great grandparent couples. What you look for in that new list of matches are third cousins who might be related to Jane’s parents (light blue) or 4th cousins who might be related to Jane’s grandparents (dark blue).

We do this by using the Shared Matches tool (AncestryDNA, MyHeritage), or the In Common With tool (Family Tree DNA) which helps to pull out of your match list only those who are sharing DNA with you and one other person. In the video below, I demonstrate the In Common With tool at Family Tree DNA (except that now to get to it, you have to click on the box beside the name of the person you want to use in the tool, then choose In Common With button located at the top of the match page.):


DNA testing just for fun?

For those of you who are testing not to address a particular hole in your tree, but just as a document of your family line, (and to join the genetic genealogy party!), your testing strategy should be to gather autosomal test results from second cousins from each of your known ancestral lines at the great grandparent level. You should also consider finding a direct paternal line descendant of each of your four great grandfathers (dark green) to take a YDNA test from Family Tree DNA to represent the surnames of each of those lines. The YDNA provides a record of these direct paternal lines can help you sort out how different lineages with the same, or similar surname are related, among other things.

Keep recruiting your relatives to be tested. The more you know, the more you learn. Gradually you’ll chip away at those genetic genealogy mysteries. If you don’t have a specific question on your mind yet, you’ll probably eventually come across one, and you’ll be better prepared to address it.


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