Wednesday, April 20, 2016

Another interesting DNA dilemma

I have a total of 10 people that match on chromosome 17 with the same starting position.  The segment lengths are 9.84 to 113.89.  I have two known family groups represented.  My uncle and I are one known match.  The other group is a man, his mother and his known 2nd cousin.  The other people in the group have no known connection so far.  Everyone is a non X match. If everyone had been an X match it would have helped narrow down which line it could be. When all 10 are put in a Matrix everyone matches everyone else except one person matches everyone else but one.  This is an almost perfect Matrix.  Here is the graphic sans names.

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This tells me that all 10 have the same common ancestor. Now here comes the problem. After looking at everyone’s trees (the ones that have trees) no connection is found.  This actually narrows it down a bit more because I only have a couple of lines that I don’t have back far enough that it should pick up the match.  The other people are in the same boat. They can’t find a match to each other.

So here is my brilliant idea.  I created a group on BYU’s Relative Finder for all of the matches.  A couple already have FamilySearch logins but they don’t have themselves linked into the Family Tree.  Once I get everyone inputted, we MIGHT find the match this way.  If we do we will still need to prove the relationships up our individual chains but it is a start.

The bonus for me is that if I figure out who the common ancestor is, I can assign this segment of chromosome 17 to this ancestor. If anyone else ends up matching me on this segment, and they pass the matrix test, I will immediately know the ancestor.  They have to pass the matrix test because everyone has TWO chromosome 17s.  All of the above match the chromosome 17 that came from my father, not my mother.  How do I know?  One of the matches is my PATERNAL uncle.  If a new person is added to FTDNA that matches me on this segment I will have to make sure that they are matching me on the paternal chromosome 17 and not my maternal one.

 

Copyright © 2016 Michèle Simmons Lewis

19 comments:

  1. DNA is still foreign to me! For you, looking forward to you solving the puzzle!

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  2. Wow! Ok... I have so much to learn about DNA. I haven't ever seen a 'matrix test' before. I know I need to learn more. Hope it works out for you!

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    1. The Matrix is just one of the tools you can use on FTDNA. It shows if if your matches are also related to each other.

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  3. Your sentence about the non x match is incorrect. An x match only eliminates tree branches for the path that x segment was inherited.

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    1. Maybe I worded it wrong. If I were to do a X inheritance chart these matches would be on one of the NON X lines.

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  4. As I'm understanding this, two people could match in the same chromosome location, but if they don't match on the matrix, they could be from the two different sides, maternal or paternal?
    So, could they also show up as In Common With matches, but be from opposite sides of the family?

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    1. Each person has TWO chromosome 17s (you have two of each). If I only looked at who matched me on this location of chromosome 17 then I would have no way to know if it was on my mother's side or my father's. In this case my paternal uncle also tested so I know it is on my paternal side. When I put myself, my uncle and the rest of the matches they match both of us and everyone else so these matches are also paternal. If I had put someone in the Matrix that did not match my uncle then I would suspect that the match on chromosome 17 was actually on my mother's side. It just so happens I have my mother's DNA too so I would be able to confirm it.

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  5. Wish I had my mom's DNA, too late. Have you found the In Common With matches to be helpful for distinguishing the two sides?

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    1. In Common with works well IF you have a known person on one side of the other that is fairly close. I am lucky that my mother tested and my paternal uncle. These are very close matches to me so if I do an In Commons With with someone and my uncle shows up on the list then it is my paternal side and if my mother shows up it is my maternal side.

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  6. Thank you - I think I'm understanding it better now!

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  7. Michele,

    I want to let you know that your blog post is listed in today's Fab Finds post at http://janasgenealogyandfamilyhistory.blogspot.com/2016/04/follow-friday-fab-finds-for-april-22.html

    Have a great weekend!

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  8. — You said, "One of the matches is my PATERNAL uncle. If a new person is added to FTDNA that matches me on this segment I will have to make sure that they are matching me on the paternal chromosome 17 and not my maternal one."

    How would you do this? If they match on this chromosome, how would you know they are on the paternal, and not the maternal one?

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    1. I have my paternal uncle's DNA but I also have my mother's DNA. They are not related to each other in any way. If someone matches me on my mother's side they have to match my mother. That is how I can tell if the chromosome 17 match is on my material strand of DNA or my paternal strand.

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    2. Thank you, Michele! Am I correct that unless we have a clear link to a known maternal or paternal ancestor, we wouldn't know which chromosome was the paternal or maternal one?

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    3. You can still do it without a mother or a father testing. It is harder but still doable. You need to track as many cousins as you can. If you can verify their connection on paper you can then start comparing their DNA to each other as maternal or paternal. Also, you can use FTDNAs Matrix tool so show you who is related to whom (in your matches) as well as the In Common With and Not In Common With to further help you get people divided into Maternal and Paternal. If you have your DNA uploaded to Gedmatch there are even more tools up there.

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