I’ve been playing around with DNA Painter, which is a nifty little tool to help triangulate DNA matches. You create a profile and then paste in the chromosome matches from FTDNA or Gedmatch (or any of the others, except Ancestry). The latter is still lacking a chromosome browser so unless you can persuade a match to upload to Gedmatch, you can’t add these people. When you add a new match, you are given the option to say how you connect, if you know. Each of the colours in this image to the right (click on it to open bigger) represent a set of my great-grandparents, or great-great grandparents where I have known matches. I’ve excluded my closest matches (mother, brother, aunt and great-aunt) because they would share too much DNA to be helpful for this exercise. In particular, my mother and brother would each share 50% of my DNA. But these more distant matches, 4 of whom represent a cousin on each side for each of my parents, help me divide the shared DNA and divide up my matches into my four sets of great-grandparents. These four cousins show quite diverse amounts of shared DNA. The usual range for a first cousin once removed is a broad 141-851 centimorgans*.
Maternal grandmother side 1C1R: 502 cM
Maternal grandfather side 1C1R: 231 cM
Paternal grandmother side 1C1R: 391 cM
Paternal grandfather side 1C1R: 194 cM
I share more with my 2 grandmother’s sides than grandfather’s. They’re all well within the range but it amuses me to note that my favourite one of these cousins is the one who shares the most DNA with me!
The other use for this tool is to see where unknown matches overlap with known matches. If you can pin down a match to your mother or father’s side and it syncs with a segment of known DNA, then you can say with confidence that you share a common ancestor on the same line. Ultimately, it will be possible to say which segments of DNA come from which ancestor or at least which ancestral couple.
The current profile depicted here represents 19% of my DNA. I hope to post an update with more added in the coming months.