DNA Segment Triangulation
By Kitty Cooper
Blogger
blog. kittycooper. com
What is a DNA segment?
Ancestry DNA can be uploaded to any or all of these sites to see segment matches in a chromosome browser:
- GEDmatch.com
- MyHeritage.com
- FamilyTreeDNA.com $
5 cousins compared, but do they match each other
Data from the ISOGG wiki at https://isogg.org/wiki/Identical_by_descent
ISOGG wiki entry for Triangulation
https://isogg.org/wiki/Triangulation
Triangulation
- When three people all match each other at the same autosomal DNA location we call it Triangulation.
- From ISOGG: "If you have at least three people with a common ancestor matching on the same segment then you can infer that the segment came from that ancestor. "
- Inversely, if three people all match each other on the same good sized segment then you can infer they have a common ancestor.(larger than 7cM but 11cM or bigger is preferred)
Blaine Bettinger's DNA relatedness chart, from his site http://www.thegeneticgenealogist.com/
August 2017 chart is at
https://thegeneticgenealogist.com/wp-content/uploads/2017/08/Relationship_Chart_FINAL_August_2017.jpg
George
Anna
Anton
Anna
Henry
(me)
GGG
GG
G
GGG
GG
G
KRISTINE v my cousins
Kristine compared to Mike and John on chromosome 11
John
versus
Mike
Chr 11
Kristine compared to John, George and Henry
John versus 2nd cousins
George (PG) and Henry
Chr 14
(George)
Kristine compared to Mike and Katy
Mike versus Katy
Chr 16
GGG
GG
G
The total number of cMs seemed low until I realized that she was from a different wife of Charley so a HALF 1C2R
Only one of the five segments MM shares with Kristine is in the same location as the other cousins, the one on chr 11, does it triangulate?
Kristine compared to Mike and John on chromosome 11
John vs Mike
Chr 11
WOLD homestead 2015 in Vestfold, Norway
Questions?
Make a Master Spreadsheet of your segment matches
Template available in my downloads area http://blog.kittycooper.com/?ddownload=2556
GenomeMate is another way to organize this data as is DNApainter.com
Every company but ancestry will give you the segment information in this format or similar - you can cut and paste into your spreadsheet
Add the columns you need, Match name, GEDmatch number,MRCA ...
My fourth grandparents lived on VE farm in Etne , Hordaland and I have a triangulation group for the cousins descended from them
I told Shelley she triangulated into that group very small so probably too far back to find. She replied my great grandmother was Anna VE ... so I found that we are 5th cousins once removed
Decided to investigating LuAnn, a new match with a surname of interest, Brekke
Another way to triangulate is to use other known relatives. Sometimes my brother and I got opposite side segments from Dad
These are my dad's matches: Everyone marked M for maternal matches my brother Shipley, but the P for paternal matches me
Since LuAnn matches Ship and Lester she must be maternal and since my brother matches Katy here, she is related on the WOLD line
M
(Chromosomes without matches removed)
Gunnar versus my brother
Top matches Dad has in common with Gunnar
Gunnar versus Kitty, no match on 2, match on 20
Dad's Matrix Matches
How to get a Chromosome Browser Results (CBR) file from Family Tree DNA for the DMT tool
DMT output as a CSV
DMT output as a CSV
Automated Triangulation Tool at GEDmatch.com
GEDmatch triangulation sorted by chromosome location
Gedmatch Triangulation for Dad sorted by Match Name
Cousin Katy
Gedmatch Triangulation for Dad cut and pasted to a spreadsheet then sorted by chromosome and start
Blog.KittyCooper.com