BIG Y Results Revisited

As I still await my own BIG Y results I continue to explore the results of others to familiarize myself with the test reports. In this post I am examining the report of a man with whom I have long had close STRs matches. His surname is different than mine but the STRs results suggest we share a common direct paternal ancestor in genealogical time.

In earlier testing over the years we had experienced 35/37 matches and 64/67 matches. By 111 STR markers we have 9 mismatches our unadjusted probabilities of sharing a common match according to FTDNA's TiP:

"In comparing Y-DNA 111 marker results, the probability that he and David Ray Dowell shared a common ancestor within the last..."

COMPARISON CHART

Generations	Percentage
4	1.74%
8	27.31%
12	67.71%
16	90.54%
20	97.93%
24	99.63%

Since both of us have pretty good paper trails that seem to rule out a common male ancestor within the last 8 generations, we can refine this to run the probabilities again taking this into account:

COMPARISON CHART

Generations	Percentage
8	11.54%
12	60.70%
16	88.49%
20	97.48%
24	99.55%

We have long ago reconciled ourselves to accept that we do not have a common ancestor on this side of the Atlantic although both of us have deep colonial roots. On the other hand it appears likely that we do share a common paternal ancestor within several generations before our separate departures to the colonies.


As I reported in my first attempt to find genealogical relevance in BIG Y results, I had previously done a single SNP test for DF13 but had not been able to find any more recent SNPs. My STR match had not confirmed that his DNA had progressed down the trail from L21 to DF13. We both strongly suspected that it had but it would be nice to verify this.

Verifying that he was also DF13 turned out to be a little more difficult than I thought. The indexes to BIG Y results did not include DF13 although that SNP has long been in use for the major subdivision of the large R-L21 project and FTDNA has long (at least in genetic genealogy terms) offered a single SNP test for it.

So I turned to a list on Facebook and posted a query asking if there was another name for DF13. Bob Dorr quickly came to my assistance by reposting:

"If you have tested with FTDNA as DF13+, and you search your FTDNA Big YI report for “Known SNPs” for DF13, you will not find it. You have to search for its CTS synonym CTS241 which you will find." from https://groups.yahoo.com/.../conversations/topics/20249  

It then occurred to me that I could have found this information in the ISOGG YSNP Tree. CTS241/DF13/S521 are all listed as synonymous there. So many new SNPs have been loaded recently that you may have to give the page a moment to fully load. Then you can use the "Find" feature of your browser to search for a particular SNP.

Mike Wadna soon chimed in on Facebook with this piece of intelligence:

In some cases, the test read quality was low, so it will be marked as REJECTED even though it is derived/positive. The only way I know to check that is look in your raw results. DF13/CTS241's position # is 2836431 and this is the allele change, A to C.

   
So with this information in hand I was able to decoded my match's BIG Y results and determine that he too was positive for DF13/CTS241/S521. I emailed him and said, "So far that was a very expensive individual SNP test you took. ;-)" $495 for BIG Y is considerably more than an individual SNP test for $39.  However, the fun of decoding was only beginning. 

I have subsequently been able to locate BIG Y results for 12 SNPs that have been placed just below DF13 by the R L21 project team. They were all negative for my match who is serving as my temporary surogate. I'm still investigating 2 that had "?" calls and a few more that I have yet to locate in BIG Y. At this point BIG Y is becoming cost effective. Thirteen SNPs tested at $39 each would run $507. Every thing else is gravy. The fun of analyzing BIG Y results is just beginning.  

Even one more step from DF13 downstream to be closer to the present would be very exciting – at least for a couple of hours. Then we would start clamoring for more downstream SNPS!

Hope the thousands of you who ordered BIG Y are enjoying your results.