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Using your Y-DNA results

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Written by Kimberli Faulkner Hull
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© Kimberli Faulkner Hull

To begin, let’s review Y-DNA at a high level. Y-DNA is frequently associated with the surname because it follows the patrilineal line. If your family tree/pedigree chart is horizontal, with you on the left, the patrilineal line is on the upper, outer edge – the one with your father, his father, his father, and so on. Males pass down their Y chromosome to all of their male children, who in turn pass their Y chromosome to their male children, and so on, and every one of the males from your patrilineal line have nearly identical Y-DNA.1

Patrilineal line

For example, all of your male cousins that are sons of your father’s brothers have the same Y-DNA as you. All of your second cousins that are sons of your father’s father’s brothers also have the same Y-DNA as you as well. It’s key to remember though, Y-DNA does not pass from fathers to daughters. If you go back through your tree identifying those who would share your Y-DNA, only include sons of sons and not sons of daughters and only members and descendants from your patrilineal line.2

Surnames and Y-DNA

Surnames are related to Y-DNA – you can see from the above examples that all of the males in that line would typically share the same surname.  In cases where a male’s surname is not known at some point in the patrilineal line, the Y-DNA test can provide clues as to what that surname may be by viewing others with similar or very similar Y-DNA.3

At this point, it is time to head to your FamilyTree DNA (FTDNA) Y-DNA Matches page. Reviewing matches requires understanding a bit about the Y-DNA test itself. The type of test used by FamilyTree DNA is what is called a Short Tandem Repeat or STR test. On a 111-panel test, 111 STRs were tested, also called markers, on your Y chromosome. At each marker are nucleotides, represented by the letters A, C, G, and T. The order, absence, or insertion of those letters at each of the markers on the Y chromosome is what makes up your results.4

FTDNA then compares your results to those of others that have tested and the closest matches are listed on your Y-DNA Matches page. Many matches will share the same surname and many will most likely have reported an ancestor with the same surname.

Y-DNA matches

Family Tree DNA mtDNA matches, names removed
Family Tree DNA Y-DNA matches, names removed where appropriate

The above image shows my spouse’s four top Y-DNA matches. He has tested at the Big Y 700 level.

  • The first is a Hull surname match (given name removed for privacy), 4 steps genetic distance tested at 111 markers.
  • The second is a match using the German form of the surname, Holle, again 4 steps genetic distance, tested at 111 markers.
  • The third is a is a Hull surname match (given name removed for privacy), 6 steps genetic distance tested at 67 markers.
  • The fourth’s full name, including the surname was removed for privacy as it was not Hull, 6 steps genetic distance tested at 67 markers.

Let’s continue with the information on the Y-DNA Matches page. Across the top, you will see the types of tests taken by your matches (111, 67, 37, etc.) and the test takers who took each test. From the information provided, you will see their predicted haplogroup and possibly the name of who they believe was their earliest known paternal ancestor. You will also see a genetic distance with each test taker. Let’s say you have a 111 level match with a genetic distance of eight. That means there were eight differences found when comparing your test results to the other test taker’s 111 markers.5

So, how close are you related to the other test taker with a genetic distance of four? If you click the icon on the far right that looks like a grey bar graph, the Y-DNA TiP Report displays a probabilities chart listing how many generations back you may find your shared ancestor. For example, a genetic distance of 8 at the 111-panel level is estimated that the probability of the generation where you share your most common recent ancestor is in the range of about 1.66% within 4 generations to 99.6% within 24 generations.6

If you remember back when you set up your account, you added your earliest known ancestor information.7 The information displayed for each test taker is what they entered using the same process. Keep in mind, this is user-entered information, and the sourcing quality, if any, is unknown.

How do you use that information?

I will now use a real-world example of using Y-DNA in genealogy research. My spouse’s 2nd great grandfather died in 1848 in his 30s. There is no death record, no burial location, no will. In the United States, there are four primary Hull lines – a large English one, a small English one, an Irish one, and a German one.

Using autosomal DNA (atDNA), I’d found two females living at the same time in the same county who are most likely his 2nd great grandfather’s sisters or aunts, both with no trace of a father either. However, with my spouse’s Y-DNA results, it was instantly obvious he was from the German line based on the matches (many were German). Do we now know the identity of his 3rd great grandfather? No. But, we narrowed down the list of potentials significantly.

Endnotes

1. 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.

2. Ibid.

3. Ibid, 32.

4. “FamilyTree Y-DNA, FAQs, What is a Marker or STR?,” FamilyTree DNA, (https://www.familytreedna.com/products/y-dna : accessed 12 June 2019) and 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 26-28.

5. Elise Friedman, “FamilyTree DNA Results Explained: Y-DNA Markers, Matching & Genealogy,” video, uploaded 21 Mar 2015; YouTube: FamilyTree DNA Channel, 1:55:40, (https://www.youtube.com/watch?v=ekB9LY_aL04&list=PLs5s5YNg5DCgxqGAZ1Jv_wzHVd13AjUyz&index=2 : accessed 12 June 2019).

6. “Y-DNA TiP Report, probability prediction chart for genetic distance of 8 at 111 level panel.” FamilyTreeDNA (https://www.familytreedna.com/ : accessed 22 Jan 2022), FamilyTree DNA account of Kit 901299 “Hull.”

7. “Account Settings, Earliest Known Ancestor,” FamilyTree DNA (https://www.familytreedna.com/ : accessed 12 June 2019), FamilyTree DNA account of Kit 901299 “Hull.”

Citing this page: Kimberli Faulkner Hull, author, “Using your Y-DNA results” Cool Adventures ( https://cooladventures.com/genealogy/using-your-y-dna-results/ : posted 2022).

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