Shared Chromosomes and Triangulation Part 1

The purpose of the following series, “Shared Chromosomes”, is to discuss and demonstrate how using shared matches between multiple family members can be useful in discovering on which side of one’s family, paternal or maternal, a common match resides. Once identified matches can be compared on the Chromosome Browser and used as a part of the Triangulation process.
In this, the first of a four part series, the methodology of gathering data for identifying shared common relative matches will be explained.
Part 2 will show how easy Autosomal DNA research can be when one has their parents and grandparents. This section uses the DNA of a man who has his mother, father and grandmother in his testing camp.
When one is the oldest in a family, as many are, and all older relatives have gone to the family reunion in the sky, then a “Plan B” is needed. Using Shared Chromosomes makes a good “Plan B” and that is what is discussed in Parts 3 and 4.
Part 3 demonstrates how I used myself, my brother, my sister, two 1st cousins and 2 2nd cousins to predict on which side of the family, maternal or paternal, one should look when there is a shared match between two or more members of the family unit.
In Part 4, X-chromosomes are discussed. Using shared X-Chromosomes between family members and those matching those family members, one can hone in on possible locations on a pedigree chart from where shared matches might emanate.
The use of the Triangulation process is touted as being the best method to establish common relationships to ancestors or ancestral families. Triangulation means the DNA of at least three people/cousins are compared and matched on at least one chromosome at the same place or places on at least one chromosome.
Triangulation is accomplished using one’s personal Chromosome Browser on Family Tree DNA or 23 and Me where the chromosomes of the person testing is resident on the Chromosome Browser. Next, one adds a cousin of known relationship to the Browser. Then a third (or fourth or more) match/ cousin is added. The goal is to match the known cousin and the new cousin(s) at the same place on the same chromosome. Thus, there is Triangulation.
Discovering which cousins to use to Triangulate can be a long and tedious process. Normally, on Family Tree DNA, one uses the “in common with” method to identify strong candidates for potential Triangulate matching. Those matches not making the cut are discarded as not being useful. A similar “Match” tool operates on 23 and Me. There is no current tool available for AncestryDNA.
There are at least three methods of mining for potential Triangulate cousin matches useful to the researcher. All are long and laborious processes.
1) Possibly the most common method of discovering relatives on Family Tree DNA is using the “in common with” and the “not in common with” filter. Once “in common with” matches are identified they need to be analyzed in the Matrix tool to see if one cousin matches another. Sometimes they do, sometimes they do not. Those that do can be further used and those that do not are discarded. From the Matrix matches are compared in the Chromosome Browser. If the Chromosome Browser shows the matches on the same chromosome at the same location those cousins can be deemed matching and the cousins deemed to be from the same ancestor or family.
2) The second method involves downloading into an Excel file or files the start and ending markers and the number of segments and their cM size or whatever comparative items of data one might choose to use. Once the data is downloaded the data would have to be sorted by chromosome and then compared to the data of known cousins. Because most matches have numerous chromosome segments the file or files would be humongous.
3) The third method is also a long and tedious procedure. I call it “Shared Chromosomes”
The biggest detractor of this process is financial. It entails getting as many relatives as possible involved in DNA testing. The detractor is not getting the relatives to test, it is having to pay for those relatives who are reluctant or not interested in testing but will test if you pay for it. If enough cousins are interested they could pool their funds and offset the financial burden on one or two family members.
Below is the Shared Chromosomes operational process which identifies the side of the family- maternal or paternal- matches of chromosome relatives can be found.
1) On March 13, 2015 this researcher downloaded into a single Excel file all matches from my personal ”Matches” page. I continued downloading the matches of my brother, my sister, two 1st cousins and two 2nd cousins. A total of seven people.
The following Excel fields were created:
a) Last name of the match
b) First name of the match
c) The email of the match
d) The Y and MtDNA haplogroup, if, in the file
e) The relationship to the person whose file was being downloaded.
2) An additional columnar data field was added to the right side containing the name of the familial person whose file was being downloaded.
3) All data was sorted alphabetically by surname, then by given name
4) For esthetics, to give break lines, clarity and space to the list this researcher went through the list placing spaces above and below matches having more than one or more of the seven family members. In other words, if a match matched one or more of the seven family members in the group, a space was inserted so the matches were clearly visable to the eye. It also reiterated the concept and use of the word “Shared Matches”
5) The resulting list was 270 pages long containing 7987 individual matches.
6) Lastly, each match between family members was manually counted and totals calculated. Those totals are given in the narrative of Part 3

A similar list of X-Chromosome matches for each family member was created in a new combined Shared X-Chromosome file in the same manner as above. The results of this file are posted in Part 4.
As anyone who has been at least somewhat successful trying to identify one’s DNA matches and attribute them to common ancestral match can attest, what was done in this project or in any other is a long and tedious journey.
This article does not contend the Shared Chromosome process is the very best method to identify relatives but it has worked quite well for me. While long and tedious this process helps identify the side of the family on which a match is located and shortens the track to where Triangulation can be utilized.
It is hoped the Shared Chromosome process method will help others’ search easier and faster than it might otherwise be.

Using Chromosome Browsers and Triangulation have been extensively written about in numerous blogs.

Following is the list of links to some blogs and articles about Triangulation. I urge everyone to subscribe to each of these blogs and learn from each of them

Roberta Estes: http://dna-explained.com/2013/06/21/triangulation-for-autosomal-dna/
Kitty Cooper: http://blog.kittycooper.com/2015/02/triangulation-proving-a-common-ancestor/
Blaine Bettinger: http://www.thegeneticgenealogist.com/2015/05/29/the-shared-cm-project/
Randy Majors: http://www.randymajors.com/2011/05/how-i-use-family-tree-dna-and-23andme.html
Ann Turner: https://drive.google.com/file/d/0B-wpDkkP5x0odkFRdDFaNHloOFk/view?pli=1
Jim Bartlett: http://segmentology.org/how-to-triangulate/

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