From STRs to SNPs – An update on my yDNA Testing

Back in 2014 one of my earliest blogs was about my yDNA testing (If you remember your school biology, yDNA is the sex-chromosome that sons get passed, virtually intact, from their father, daughter’s get a second x chromosome). Things have moved on since then, so I thought today would be a good chance to update this. I also want to use this blog to explain the processes I went through to get further information on my paternal line.


My GGG-Grandfather was Henry Grass (1764-1845). He is recorded as “Base born” i.e. born outside marriage. His mother, Elizabeth Grass, was a widow and we have no record of who his father was. I’ve been hoping that by having my yDNA tested I will find a match descended from an earlier, common paternal-line, ancestor of both myself and my match.

In 2014 I had the results of a 37 marker yDNA test. They were rather disappointing. No matches at the 37 marker level, suggested that there was no-one on the FamilyTreeDNA  (hereafter ftDNA) database that shared a recent common, direct-paternal-line, ancestor.

More STR Testing

Last year I upgrade my yDNA STR test (Short Tandem Repeats – remember) to 67 markers. The rational being, that sometimes you have a close match at 67 markers who may just have enough mutations at the 37 marker level not to be matched at that level. Sadly no-one matched me.

As a result I thought it was time to switch track a little and look at my yDNA Haplogroup. As the ISOGG wiki nicely defines it:

A haplogroup is a genetic population group of people who share a common ancestor on the patrilineal or matrilineal line. Haplogroups are assigned letters of the alphabet, and refinements consist of additional number and letter combinations”

You may find some companies marketing haplogroups as “tribes”, such as Vikings or Picts. I hate this simplification. Personally I doubt that all members of any of the recent (i.e last 2000 years) historical peoples were descended from a single source. I find it far more likely that “tribes” were much more mixed, as people joined in/were invaded/were made slaves etc.

(Sorry if I was ranting there, back on-topic). Haplogroup information can be used to make a phylogenetic tree, identifying branches based on mutations of the yDNA from a common root (in this case the y-Chromosomal Adam). The International Society of Genetic Genealogists maintains such a yDNA tree.

My basic Haplogroup results were found from a DNA test I took as part of the National Geographic’s Genographic Project. There I was found to be I-Z138, as the graphic below shows:

This branch of Haplogroup I makes me among a mere 1% of the men who've taken this test.

This branch of Haplogroup I makes me among a mere 1% of the men who’ve taken this test.

At this point I should mention that that there is an old and a new format for yDNA Haplogroup names. Originally Haplogroups were named in an alternating Alphabet/Numeric pattern, based on the branching of the tree. For example I-Z138 is sometimes referred to as I1a2b. Over time this naming structure has proved unwieldy and is now being replaced by a basic Haplogroup (I in my case) followed by the final, defining SNP. A SNP being a Single nucleotide polymorphism – a mutation at a defined point in our DNA.

Let me try and put this in context. I-Z138 is a “sub-clade”, or branch, of I-M253 (or I1 in old terminology). I1 is most-often found in Fenno-Scandia, but also, with decreasing frequency, throughout the rest of Northern Europe. It is often “associated with the Norse ethnicity” and is normally assumed to come from early European hunter-gatherer populations. The “Time to Most Recent Common Ancestor” (commonly known as TMRCA) for I-M253 is estimated as 4,700 ybp (Years Before Present), however it’s estimated that the mutation occurred sometime between 45,700 and 40,300 ypb. The vast difference in time is due to the fact that a small population basically got stuck, or “bottlenecked” during the “Last Glacial Maximum”. This resulted in the same small pool of genes being continually recycled through the generations, with occasional mutations occurring in the yDNA. As a result Haplogroup I1 is “defined by at least 25 unique mutations“. By contrast, my haplogroup, I-Z138 has a TMRCA of 4,400 ybp, but was formed around 4,700 ybp. Remember these are all rather fuzzy estimates.

Back to me. Knowing that I was I-Z138 I joined the I-Z138 project at ftDNA and the I-Z138 Project’s Facebook group.  This is an incredibly useful and knowledgeable group of people who, as the name implies, are researching and refining the whole I-Z138 branch.

In addition, earlier this year I stumbled across a website,, which takes your STR data and predicts your Haplogroup from this data. I must admit I know very little about this site, but there is plenty of background reading for those interested.

Entering your yDNA data on is actually quite easy. So, if anyone with yDNA results, wants to try the site just do the following 4 steps:

  1. Sign in to and go to your results page.
  2. Download your results as a .csv file by clicking on the CSV button at the bottom right hand side of the page.
  3. Find the .csv file you just created using “File Explorer” (Windows 10) or Windows Explorer (Windows 7). Right click and select the option to “Open with” Notepad.
  4. Copy and Paste the second line of your csv file into the box on marked “Enter your results as follows”, then click on calculate.

Following the above procedure I got the following result (along with some statistical analysis, which I won’t bore you with).

The result of my yDNA 67 marker data in

The result of my yDNA 67 marker data in

The result couldn’t have been clearer. I was predicted to be I-Z2541, which is a downstream (i.e. a more precise) sub-branch of Haplogroup I. It also implied that I was positive for the intermediate marker S2293.

Testing at

To test for individual markers within the y chromosome you have two main choices, either through or through Germany’s very-own testing lab set up by geneticist Dr.Thomas Krahn. Since my needs were very specific I went for the German option (available at $17.50 or €13.92 per SNP). The results arrived approximately one week after testing. I was indeed positive for both S2293 and Z2541.

These successes inspired me to do further testing. The I-Z138 Project, that I mentioned earlier, has quite a detailed phylogenetic tree for their sub-branch. As a result I could see that downstream of Z2541 there were 2 main branches (S2268 and Y7043 if you’re interested). On a whim I tested both. The result is that I’m now I-S2268. Currently, this is the end-point on my personal yDNA journey.

Final Thoughts

I’m pleased to have got this far with my haplogroup testing. I hope that through testing, I’ve somehow contributed a little to the research in this area.

There is nothing I can really test that would further define me within the I-Z138 phylogenetic tree. The only other options would be to do go for one of the major yDNA tests, such as the Big Y test. This would normally identify virtually all relevent yDNA SNPs, including, potentially, private SNPs unique to my family line. At around $500 this is not a cheap product and not one I’m currently ready to invest in.

I’m now in a group of one within the I-Z138 project, based on the combination my SNP and STR results. Basically I’m an outlyer. I’m hoping that, eventually, others will join me in this group.

Among the few, distant, relatives I have from my STR results, 2 have Danish ancestry.  Based on this, and my own Suffolk patrilineal line, I wonder if my ancestors may be associated with either the Anglian or Danish Viking invasions of Britain, although I doubt the real story is so simple.

This entry was posted in Genetic Genealogy, Uncategorized, yDNA and tagged , , , , , . Bookmark the permalink.

2 Responses to From STRs to SNPs – An update on my yDNA Testing

  1. Pingback: My LivingDNA Test Results | learnalittleeveryday

  2. Pat Davis says:

    I’m also folo’g I-Z138, for my DAVIS cuz… yDNA matches with SCHWEITZER (SWITZ, GER) … CORBIN (ENG)… BOGAERT (NETH)… DAVIS migrated thru early WinchesterVA area, Old Frederick Co., from near early NYC… to seOH, 1810 census.

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