Thursday, March 1, 2018

MyHeritage Leads to Progress/Matching Problem Found

I've been collecting DNA segments since I first took the atDNA test in 2012. I first tested with Family Tree DNA which provided the segment data which allowed me to begin this process. I then uploaded that data to GEDmatch and was able to add a few more segments to my chromosome segment map. A few years later I tested with 23andMe. Initially all of these sites provided me with a number of additional segments. After the initial finds from a new database adding segments became very slow. The matches at FTDNA are often low quality and don't have any surnames or trees posted. Once every few months I have found a segment or two to add to my map at FTDNA. Same with GEDmatch. Most matches at GEDmatch have no tree posted. Sometimes you can find them with a tree at Ancestry. Often the GEDmatch Ancestry matches use a different username at the Ancestry site. 23andMe has helped me add a few segments to my map. The biggest problems at 23andMe are no trees, lack of response to messages, and little family knowledge of those testing. The tools are great at 23andMe, but without trees making connections is difficult.

Thank god for MyHeritage which provides trees, a chromosome chart with shared segments, shared match information, and shared surnames all on one page for ease of reviewing matches. Instead of adding segments, or a couple of segments, every month or two I'm adding half a dozen every week. I'm not sure everyone would see the same results? I have a feeling that is because some of my ancestors immigrated to America more recently? Although I have found some good matches with early colonial southern ancestors. I'm getting so much of a good thing I'm having trouble keeping up with all the new segment data.

You can see my most recent chromosome map above. I've marked the segments with names using Paint. I used Genome Mate Pro to create the map. It's actually better to make separate maps for the maternal and paternal lines so you can use the extra line space to write the names.

Filter chart by paternal and maternal allows more space for names


Matching Problem Found

It seems my mother and I have continuous problems with one particular match on our Browning line we'll call CPE. This match is a 2nd cousin 1x removed for my mother. The first problem with this match was the fact she was eliminated as a match at Ancestry when they introduced the Timber filter. This cousin, according to FTDNA, shares one 36.69 cm segment and two others. The other two segments are 14.89, and 13.68. Can you imagine this great match was eliminated? She did reappeared later when Ancestry performed some sort of update that fixed some of the Timber problems.

Adding segments I noticed someone, we'll call DPA, matches me on chromosome 15 with a  13.2 cm segment, and matches my mother beginning at the same start point with a longer 35 cm segment. Family Tree DNA considers our cousin DPA, with my 13.2 cm matching segment, to match both my mother and I. Our CPE cousin from Ancestry, overlaps my mother, DPA and I exactly on chromosome 15. That would mean I share around 13.2 cm's with CPE. This conclusion is reached by comparing the red segment I share with DPA on chromosome 15, with the dark blue segment of CPE (see chart below). However, even though I share a 13.2 cm segment with our Browning cousin, CPE, I don't show up as a match at either FTDNA or Ancestry?  Since this person isn't Nicaraguan at all the 13.2 cm segment  I share with CPE can't come from my maternal grandmother Graciela Del Castillo. Instead it would have to come from my Northern European Grandfather Charles Forgey whose uncle William Jefferson Browning is this matches direct ancestor. As a matter of fact DPA and CPE are both descendants of William Jefferson Browning, which is why they share overlapping segments with us on chromosome 15.

So how come I'm not considered a match to CPE at either Family Tree DNA or Ancestry, and her cousin is? In the case of FTDNA it's likely that CPE didn't share enough total cm's. Above you can see some of the segments I share with DPA in red. Apparently I shared more total cms with DPA, who is considered a match.

Ancestry has a different criteria for establishing matches. They cut down the size of segments based on areas considered false positive regions. The area on chromosome 15 where we share segments with our Browning cousins has a false positive region of around 2 cms. Every company has different starting and ending points and slightly different segment sizes (except Ancestry which can have large segment size differences). The false positive region could be why we've had so many problems with this match. You can see the many segments in the false positive regions which Ancestry likely considered a pileup region (chart right).

Since all of these segments, my mother, Browning cousins and mine, overlap and we all share the common ancestors Nathan Browning and Obedience McPike, and these two matches share an even closer Browning ancestor, I believe my shared segment with CPE should be considered a match. It's possible for a false positive region to be part of an identical by descent segment.

Cutting out matches who share DNA in a false positive regions eliminates thousands of false matches, however, it also eliminates a few good matches. That's why Gedmatch is important. It doesn't eliminate all of these false positive region matches and allows you to see all matching segments.

We all need to keep in mind that possible cousins may not appear as matches for a variety of reasons, and may still share matching segments. Comparing at a variety of sites can uncover matching segments, and cousins, not surfacing elsewhere.

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