Wednesday, January 10, 2018

Tara, Her Paternal Grandmother, My Cousin Kay and Others

This is the second of at least three posts regarding my families' matches with a young woman named Tara in Toronto. I discussed her matches earlier and now we have results from both her mother and her paternal grandmother. I will discuss her mother's matches in a few days, but there is something else I wish to address first. (My mother used to say that "a few days" means less than a week. No promises.)

Chromosome 8
Using the GEDmatch basic one-to-many tool, on chromosome 8, Tara matches my brother and my sisters Amy and Jean on identical segments of about 12.6 cM, the range being 96,812,006 - 107,594,161.  My sister Sarajoy is on the same segment with 9.8 cM that ends in the same place as the other three, but starts a bit later.

The triangulation is a bit odd as everyone matches on the appropriate segments except Dan and Sarajoy. It is not clear to me how that happens, but that is not what I am getting at.

I then ran the Matching Segments Tool for Tara and found a surprise. My first cousin Kay (our mothers are sisters) is on the same segment almost exactly matching Dan, Jean and Amy. But she hadn't been on the regular one-to-many. And the fancy Tier1 one-to-many has the same result as the old reliable.

The Matching Segments result for Tara is here on the right.

Kay triangulates with my brother and all three sisters on that segment of chromosome 8.

Kay should show up as a match to Tara on the one-to-manys and she doesn't. Something odd is happening at GEDmatch. Perhaps it is because this is the only segment on the twenty-two chromosomes where Tara and Kay match, though I don't know why that should matter..

So now Tara has the results for her paternal grandmother, whom we shall call Ida. Ida matches my brother, my three sisters and Kay on the basic one-to-many slightly more than does Tara. (Perhaps the fact that Ida has two segments with Kay comes into play here.) But Ida does not match Kay on the Tier1 one-to-many. On the other hand, Kay shows up in Ida's Matching Segment results but Sarajoy does not.

There is a lot of inconsistency here and it all seems to lie at the door of GEDmatch. If nothing else, it appears that we must check both one-to-many tools as well as the Matching Segments every time we look at someone new.

But we do know that we have at least one common ancestor with Tara on my mother's side of the family. Unfortunately since none of my second cousins match Tara on this segemnt of chromosome 8, we cannot break it down any further.

Chromosome 23
Another GEDmatch mystery involving Tara and Ida is on chromosome 23, the X.

Tara has  a segment of about 10.5 cM with my sisters Sarajoy and Jean, together with my second cousin Ruth on my mother's father's Gordon/Kugel side.

Ida has Sarajoy and Jean on that same segment using the regular one-to-many - and Kay as well - but not Ruth. The four of them all triangulate so they should all match both Tara and Ida. On the Tier1 one-to-many, neither Kay no Ruth appears. On the Matching Segments tool, Ida matches Jean and Kay, but not Sarajoy.

My feelings about GEDmatch are often just like my feelings about my children. I love them, but I don't always understand them.

There will be more about Tara's matches "in a few days."

No comments:

Post a Comment