Wednesday, May 10, 2017

Gedmatch Triangulation Tree Graphic: What the Heck Am I Looking At?

Attention Brady Project members: You will find this on page two of your Workbooks. See if you recognize a kit number that matches your Brady kit # list. If you recognize a known Brady cousin whose is not a member of the Brady Project, please contact them and ask them to join. The "user look up" tool mentioned in this blog will provide their contact email. (They can also be found on your one-to-many page by using Ctl+F and entering their Gedmatch kit #.)

For those who are reading from outside U.S. The use of the # means number. When referring to a Gedmatch # I mean the Kit + the alphabet letter designating what testing company was used, and the numbers that follow.

In January 2017, after three years of crossing my eyes trying understand autosomal DNA (All the blogs were over my head), the writers were speaking a language I didn’t understand. I was figuring how to use the interface at Ancestry and Ftdna, but had no idea what I was seeing. I knew which buttons to push on Gedmatch. I saw loads of stuff, saved much to folders, knew it was important, but was unable to put it all together in my head. Then I came across Jim Bartlett’s blog, Segment-ology. He teaches how triangulated groups work. I dug deep and donated $10 to check out the Tier 1 triangulation tools. It took me a month to even start to understand what I was looking at. I opted for another month. I began to get excited.

Word to learn=segment. A segment is a measured piece of your DNA.

 I started with Triangulation Groups Beta.

After I enter my Gedmatch # and wait about 14 minutes (I used the time to put in a load of laundry and wipe down the counters in the kitchen), a screen appears asking me what I want to see first: triangulated segments in a bar chart, triangulation tree graphic or CSV file. I opted for the tree graphic. I am a visual learner. (In the graphic below I have blocked some of the info for privacy reasons).

I stared. Cocked my head to the right, then to the left. Scrolled up and down the page.

 What the heck am I looking at???

Your kit # shows as reference in a rectangle over a column on the left of the screen. There are more stacks of rectangles vertically down the left of the page. Kind of like the trunk of a tree. 
The match in the lower box is in a different TG and only matches with others who share the same spot as highlighted on Chr 1 
Inside the trunk are more rectangular boxes that contain bold black lines. Each bold line represents a chromosome. Only Chrs 1-22 are represented in the box. (The X chromosome in not represented in triangulation because it doesn’t behave like other chromosomes. Scientists are still trying to figure out why and what it means.)  There are places on the chromosomes highlighted with spots that are green. A Chr number is written in the box. There is also a TG (triangulated group) identifying number in the box. The TG represents a position on that chromosome where you and at least two other people share DNA in the same spot.

To the left of the graphic tree is a blue line reaching out. It represents a tree branch and leads to another rectangle. This box contains your matches information: Kit #, user name, the Chr on which you both share the largest segment and the size of that segment. 

Some of your matches share DNA with you on more than one chromosome. When this happens the graphic will show more than one green highlight in the box. This indicates the other places they share DNA segments with you.

If there is a little tree icon in box of the match person on your branch, it means there is a (gedcom) tree in the Gedmatch database that can be reviewed and it links to this person. (You can find the gedcom number by using "user look up" in association with their Gedmatch #. "User look up" is found on the first page of your Gedmatch account, on the left hand side of the page, in the box under the heading Learn More.)

The position of blue line leading to the rectangles to the right of your chromosome tree is important.

If the blue lines connect several boxes in a straight line stretching to the right, you will notice these matches share only one segment with you, and it is in the same position on the same chromosome.

In some cases, the blue line jogs down from one box another. If you compare the green highlights in the chromosome boxes in the tree trunk, you will notice more than one highlight in the upper chromosome box and the match beneath shares a different segment in common with the reference (person who is trunk of the tree). On the right the person in the branch above and the person who jogs down the branch are related to each other. (

Study the user names and Kit# in the rectangles. Do you recognize any of them? If you have already made a connection with one of the people linked to you in this tree, the others that connect to them will share the same common ancestor (CA). BE CAREFUL. IT MAY NOT BE WHO YOU THINK. All people have to verify the same common ancestor in their tree. In some cases you may have to help them find missing family in order to make the connection.

It may lead to a person further back in your tree. For instance, my cousin, (I'll call her Clair) shares a common set of grandparents with me. They are William B. Brady and Catherine Wakefield. Clair descends through one of their children, I descend through another one of their children.  There is a third person in this graphic tree that connects with Clair and me. I'll call him Sam. Sam is the key to our common ancestor who gave all of us the piece of shared DNA in green. He may share DNA with someone higher up in the Brady or Wakefield line. It could be an ancestor I don't even have on my tree yet. I will have to study Sam's tree to find the common ancestor we all share.

It has been suggested by another genetic genealogist, the numbers at the bottom of the rectangle of known matches is due to the Beta nature of the program and does not relate to triangulation.

I have updated this post. I previously referred to a TG as a Target Group. That is because these are the people I "target" with emails to see if we really do triangulate to a common ancestor. 

Hopefully this post will give you an idea of what the heck you are looking at when you study the Triangulation Tree Graphic.


  1. Per your request for corrections and suggestions, I have already commented once that triangulation is spelled wrong.

  2. Lucy May, I only now spotted your post. Thank you. Would you believe I looked through the post three times? Finally spotted it in the title---duh! I really appreciate you help.