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Understanding Y-DNA testing

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Written by Kimberli Faulkner Hull
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© Kimberli Faulkner Hull

Using your Y-DNA results
Understanding Y-DNA testing

To understand your specific Y-DNA test results, let’s start with an overview of the two types of Y-DNA testing and how they relate to your reported haplogroups.

STR testing

The first is STR testing, which stands for Short Tandem Repeat. One of the best ways I’ve heard to describe this was by genetic genealogist, Roberta Estes, who said to think of it as a copier that gets stuck and reprints the same thing multiple times, then moves on.1 In this example, I will use the 111-panel test at FamilyTree DNA (FTDNA) – it is a STR test. Once the test results return, you are provided a prediction of your haplogroup. For this example, I will use R-M269 as it is my spouse’s haplogroup. If you go into your FTDNA account, then to the navigation at the top (myDNA > Y-DNA > Haplogroup & SNPs), the top of the page titled Y-DNA Haplotree most likely reads: “Your Predicted Haplogroup is [your haplogroup].”2

One thing to keep in mind with Y-DNA testing is that your Y-DNA is nearly identical to your oldest patrilineal ancestor’s Y-DNA. The patrilineal line is also called the surname line because it runs along that lineage of your pedigree chart: your father, your father’s father, his father’s father, and so on back for a very long time. It is passed down to sons intact from generation to generation except for mutations, which are typically very small changes at specific places on the Y-chromosome.3

STR tests examine markers for values at each of those locations and then compare your results to the results of others. Your results can be viewed in the Matches section of your FTDNA account. Each match provides a genetic distance, which is how many different mutations exist between you and the other person being compared. The lower the genetic distance number, the closer the match – zero is exact, 1 means there is one mutation that is different, 2 means there are two mutations that are different, etc.4

On the Haplogroup & SNPs page, you’ll see a tree structure – for R-M269, at the very top on the left it says R. That represents your furthest back ancestor in the haplotree, who lived thousands and thousands of years ago, whose Y-DNA was nearly identical to yours. At some point be sure to also check out the Y-DNA Migration Maps (myDNA > Y-DNA > Migration Maps) and learn about where and when your haplogroup began and see how the migrations occurred.5

As you scroll down on the Haplogroup & SNPs page, you’ll see lines and numbers connecting to other lines. Like a regular tree, there’s a trunk with branches, that has branches, that has smaller branches still. The branches are called subclades on a haplotree. You can either scroll down or use the search box to find the haplogroup that was predicted for you by FamilyTree DNA.6

SNP testing

The second type of Y-DNA testing is SNP testing, which stands for Single Nucleotide Polymorphism.7 SNP testing refines your results and defines your haplogroup. When FamilyTree DNA provided your haplogroup, they actually predicted your haplogroup by comparing your results to other testers’ results in their database.8 Continuing with the example, to confirm a haplogroup of R-M269, you would need have the M269 SNP tested, but first let’s continue.

Now, let’s look at other companies that may also provide Y-DNA results, such as Living DNA. Living DNA conducts limited SNP testing with their package, providing a haplogroup and subclade.9 To explain this, I’ll continue with the R-M269 example. My spouse was tested at Living DNA before FTDNA and was provided a haplogroup of R-U106.10 He then tested at FTDNA with the 111-panel test and it returned a predicted haplogroup of R-M269. To reconcile the two, I ordered SNP U-106 at FamilyTree DNA. Within a few weeks of ordering the single SNP test (U106) for him, he was listed as haplogroup RU-106 on FamilyTree DNA as well.11

If you go to the FamilyTree DNA haplotree page and search for “L121” and then “Z2976,” which are the SNP names that form the haplogroup and subclade R-2L21 and R-Z2976, you’ll find them below R-M269.12

You are now at the point where you can make decisions on if/how you want to confirm and/or further define your results by testing SNPs at FTDNA.13 As you scroll down the page, you’ll see blue “Add” buttons next to the numbers. That means you can test that specific SNP. It is also good to remember that, as stated above, Living DNA performs limited SNP testing. Additional SNP testing at FamilyTree DNA may refine/change your subclade further.  At this point, you could do one of the following:

  • Order a specific SNP test, such as Z2976. This would confirm your Living DNA-provided subclade.
  • Order a SNP pack bundle that FamilyTree DNA believes to be associated with a specific branch.14
  • Order the Big Y 700. The Big Y Test is the most thorough test offered. It is also expensive. You can learn more about the Big Y here.15

You may also want to join relevant projects, which are typically groups sharing a common haplogroup, surname, ancestral geography, or ethnic group. You can navigate to myProjects > Join A Project and search for projects..16


1. “Genetics Glossary,” Section S, Single-nucleotide polymorphism (SNP), International Society of Genetic Genealogy Wiki ( : accessed 11 June 2019).

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2. “How does Y-chromosome DNA (Y-DNA) haplogroup prediction work?” FamilyTree DNA, FamilyTree DNA Learning Center ( accessed 11 June 2019).

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3. Anne Westcott, “We have a new chip!” Living DNA, Living DNA News, 22 Oct 2018 ( : accessed 11 June 2019).

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4. “Living DNA results for Gregory K. Hull,” personalized database, Living DNA ( : accessed 11 June 2019), reporting Feb 2018, Haplogroup R-U106, Subclade R-S264, equivalent of Z156 at FamilyTree DNA.

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5. “FamilyTree DNA results for Gregory K. Hull, Kit 901299,” personalized database, FamilyTree DNA ( : accessed 11 June 2019), reporting Haplogroup R-M269, then R-U106 following order of singular SNP test for U-106 which returned positive.

6. “Haplogroup & SNPs, Haplotree R” FamilyTree DNA (  : accessed 11 June 2019), FamilyTree DNA account of Kit 901299 “Hull.”

7. “When should I take a Y-DNA haplogroup test?” FamilyTree DNA ( : accessed 11 June 2019).

8. “Why Should I Test Y-DNA SNPs?” FamilyTree DNA, FamilyTree DNA Learning Center ( accessed 11 June 2019).

9. “Big Y” FamilyTree DNA, FamilyTree DNA Learning Center ( : accessed 11 June 2019).

10. “FamilyTree DNA Surname, Lineage and Geographical Projects” FamilyTree DNA ( accessed 12 June 2019.

11. Roberta Estes, “Get the Most out of Y-DNA at FamilyTree DNA,” video, 55:42, undated, private Vimeo recording; DNA Central ( : accessed 11 June 2019, subscription required).

12. “Haplogroup & SNPs,” FamilyTree DNA ( : accessed 11 June 2019), FamilyTree DNA account of Kit 901299 “Hull.”

13. Blaine T.  Bettinger and Debbie Parker Wayne, “Genealogical Applications for Y-DNA,” Genetic Genealogy in Practice (Arlington, VA: National Genealogical Society, 2016), pages 23-36, particularly 23-25.

14. Ibid, 28-30 and “Y-DNA Genetic Distance,”FamilyTree DNA, FamilyTree DNA Learning Center ( accessed 11 June 2019).

15. “Migration Maps,” FamilyTree DNA ( : accessed 11 June 2019), FamilyTree DNA account of Kit 901299 “Hull.”

16. “Haplogroup & SNPs,” FamilyTree DNA ( : accessed 11 June 2019), FamilyTree DNA account of Kit 901299 “Hull.”

Citing this page: Kimberli Faulkner Hull, author, “Understanding Y-DNA testing” Cool Adventures ( : posted 2022).

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