South King County Genealogy Society Blog - The Shared CM Project Tool 4.0 #blog

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The Shared CM Project Tool 4.0 By MaryLynn




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Mystery Match - What To Do Next

You've checked your DNA results, possibly at a new test company, and you find an unfamiliar match sharing a large segment of DNA. While some of the companies assign a relationship, "1C,2R", that may not be accurate due to variables such as "half" siblings or cousins.  There are several tools available to help calculate relationships; one we have seen in presentations and online is the Shared cM Project 4.0 Tool v4.






You can locate yourself in the white square marked "Self" just off the center.  Relationships that share, or are descendants of one or both of your parents are in light or blue gray.  Relationships with which the most recent common ancestor (MRCA) is one or both grandparents are in green, great-grandparents are in orange.



The numbers in the squares represent the average shared cMs for that relationship as well as the low and high range.  Notice that ranges do overlap so it is also necessary to check family trees in order to make accurate assignments.




Where do we find the shared cMs?  Your testing company supplies that information as well as a "best guess" at your relationship with a match.













and the same two individuals from My Heritage:



The shared cMs are similar in range and percentage but My Heritage gives more possible relationships.  



23 and Me



23 and Me give the shared cMs as percentages and, while they give a relationship, again there are variables.


Shared cM Project Tool works with all tests

At the Shared cM Project tool, you can enter either the number of shared cMs or the percentage in order to get the range of possible relationships.





















If you enter the shared cMs as a percentage, you get the following information:

















and a chart with highlighted probable relationships:

Be sure to look carefully at all of the possibilities; don't overlook possible half relationships.




MaryLynn Strickland

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