Wednesday, January 15, 2014

The Worthwhile Autosomal DNA Segment Analyzer


I have been using DNA testing as an adjunct to my genealogy research for a few years.  I use an Excel spreadsheet of my own design to keep track of the matches, which includes which DNA cousin matches my close family members and where.  It is time-consuming to manually enter each piece of information and then organize it by chromosome for each family member and note who else matches the DNA relative.

The purpose of organizing the DNA matches is to look for patterns to identify the Most Recent Common Ancestor- the source of the segment of DNA shared by living descendants.

I was delighted to read about DNAGedCom's new tool, the Autosomal DNA Segment Analyzer (thank you Roberta), developed by Don Worth.  (In order to use DNAGedCom you have to test your DNA first.  DNAGedCom is not a testing company.)  For this particular tool, data from FamilyTreeDNA is used.  I previously uploaded results for family members from 23andMe to FamilyTreeDNA.




Above is the table produced for chromosome 13 of my father's DNA test.  The match with the longest shared segment is me, naturally, represented by a black bar the entire length of the chromosome.  We will look at a third cousin whose DNA has been tested.  He and my father share a segment that is about half the length of chromosome 13, which is a lime green line in the above table.  This segment is from one of their shared ancestors, Calvin Cook or Mary Neil, who were the great great grandparents of my father on his mother's side.  Four more people also match this third cousin on this segment, indicated by the lime green box in their ICW column (in common with).  These means that I can collaborate with these four people, compare family trees, and find a link in all four to either Calvin Cook or Mary Neil.

Next view the two people who also match my father in the same area shared by the third cousin.  The are medium blue and maroon bars in the table.  These people do not match the third cousin.  I do not match the third cousin, but I do match these two people.  This indicates that these two people are related on my father's father's side of the family tree and at least the last half of my chromosome 13 came from my paternal grandfather.  From that point backwards, we cannot tell with this information if the matches are from my paternal grandfather's father or from his mother.

The tables for each chromosome show you how your genetic matches cluster together into theoretical branches of your tree.  You need to compare documented family lines to figure out the ancestors.




I would like to point out important features.  These tables were created using information from FamilyTreeDNA.  The names and email addresses of most matches are visible to their other matches (I blocked them here for privacy).  Selecting a match's name pops up a window with additional information, such as surnames and locations, that the match has typed into his/her profile.  This is in stark contrast to matches at 23andMe, most of whom are anonymous and do not respond to requests for contact or genealogical information.

23andMe DNA Relatives/Relative Finder
Anonymous matches with little to no profile information who do not accept contact.