Sunday, November 20, 2016

So Close...And Yet So Far Away

Often people look at a match, and if that match doesn't also match cousins on one side, they conclude that the relationship is on the other side.  That isn't always a correct assumption.

Recently, I checked my uncle's kit (my father's brother) on AncestryDNA and discovered a new potential 3rd cousin match.
My uncle's AncestryDNA match with D

I've found that AncestryDNA's predicted third cousin matches are pretty decent, even when you're Ashkenazi (and therefore endogamous).  I contacted the kit's administrator, and she replied very quickly.  D is her step-mother, and she had minimal information on D's family (and the locations and places she did have didn't quite mesh with my family).  I asked her to transfer D's raw DNA data to GedMatch so that I could take a closer look.

My uncle's & D's shared DNA

Sure enough, D and my uncle shared quite a bit of DNA.  In addition to sharing five segments in the 7-8cM range, they also shared two large segments--one 18.3cM and one 32.9cM on chromosomes 20 and 14.  Things looked promising!

In order to narrow down on which side (or sides) my uncle was related to D, I looked at my grandmother's kit.
My grandmother's & D's shared DNA

My grandmother and D only shared one 9.7cM segment on chromosome 22 which hadn't been passed down to my uncle--meaning that those large segments shared by my uncle and D would have both been from my grandfather.

Well, I could narrow that down further.  Both maternal- and paternal-side cousins of my grandfather have tested; let's see who matches D.

On my grandfather's father's side, we can look at Beth, Dave & Liz.
Cousins who have tested on my grandfather's father's side

  • Beth shares only one 7.1cM segment on chromosome 3 with D
  • Dave shares nothing with D whatsoever.
  • Liz also shares nothing with D.
That doesn't look very promising at all.  So it looks like the connection would be through my grandfather's mother, right?  Many people who have only tested relatives on one side would make that assumption.  But just to be sure, let's take a look at cousins on my grandfather's mother's side.
Cousins who have tested on my grandfather's mother's side
Two of my grandfather's first cousins (George and Mitzi) have tested, as has his half first cousin Ina.
  • George shares a 7.2cM segment on chromosome 3 with D
  • Mitzi shares a bit more--four segments on chromosomes 3, 4, 5 & 6, ranging from 7.3cM to 11cM--which may be something or may just be a factor of being from an endogamous population.
  • Ina shares 7.4cM on chromosome 3 with D.
  • Note that all 3 of the cousins on this branch share essentially the same part of chromosome 3 with one another and with D, so there's at least a remote connection, but that isn't surprising in an endogamous population.
But no one shares any DNA with D on chromosomes 14 and 20, and none shares sufficient DNA with D to be compelling enough for me to investigate further.

If I looked at cousins on only one or the other of my grandfather's parents' sides, I'd have assumed that the relationship must be on the other.  But looking at both, you can see that in this case DNA doesn't help to narrow down a side.

And just to throw another wrinkle in this, I figured I should take a look at DNA shared between my father and D--perhaps my father and D would share a different large segment that would suggest a better connection to investigate.
My father's & D's shared DNA

My father also only has small segments in common with D, ranging from 7.8 to 8.9cM, none of which are on the chromosomes on which D and my uncle have those large matches.  So if I'd only tested my father (and not his brother), I'd never have investigated D's connection at all.

So where am I with narrowing down the connection to D?  At this point, I just know it's somewhere on my paternal grandfather's side.  Hopefully D's stepdaughter's paper trail will get a bit more solidified, and then maybe we can figure out the connection.  So stay tuned!

Note:  I'm on Twitter.  Follow me (@larasgenealogy).

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  1. I would run your uncle's kit on the GEDmatch Matching Segment Search, a Tier 1 tool, to see who else matches those two large segments. Who knows what might turn up.!

    1. Good idea. I'll do it the next time I have access to Tier 1 (probably when the kits ordered during FTDNA's current sale are in).

  2. Awesome! It's very crucial to focus on the largest segment. Anything more than 20cM is promising. Anything less than that is typical of an endogamous background. The more endogamous lines they have, the higher the amount of segments they will have.