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  #1  
Old 19th October 2017, 03:36 PM
B198251 B198251 is offline
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Question Confused by Gedmatch matches

Hello,

I have hundreds of matches on Gedmatch. My father has hundreds matches on Gedmatch. I match my father with more than 3000 cM on Gedmatch. But we have only 1 (one!) common match on Gedmatch. How is this possible?
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  #2  
Old 19th October 2017, 03:56 PM
karwiso karwiso is offline
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There could be several explanations:

1) Sharing DNA is a random process and GEDmatch uses default limit of 7 cM to work with matches.
Some of your fathers matches share a little bit less than 7 cM to qualify as matches both for you and your father. Try to lower limit to 5 cM, but be cautious - there could be false matches. Some matches could a quite distant relatives and than your have to work with very small cM values / short DNA patches.
2) Some of your matches are matches on your mothers side, it is possible that some of your father's matches are on his mother side. Than you would not have so many common matches? Or some other kind of cousins. Just a possibility.
3) An NPE. Well, lower than 1-2% possibility, but... probably your father is not your father. Of course you have to research more to verify that. Don't think about it first!

Other possibilities?

Last edited by karwiso; 19th October 2017 at 03:58 PM.
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Old 19th October 2017, 05:02 PM
MMaddi MMaddi is offline
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Quote:
Originally Posted by karwiso View Post
3) An NPE. Well, lower than 1-2% possibility, but... probably your father is not your father. Of course you have to research more to verify that. Don't think about it first!
There is zero chance of an NPE. The original poster shares over 3,000 cM with his father. This clearly indicates they are father and child.
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  #4  
Old 19th October 2017, 05:04 PM
georgian1950 georgian1950 is offline
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Quote:
Originally Posted by karwiso View Post
Other possibilities?
Yes, The genetic genealogy establishment has given us a faulty autosomal DNA matching methodology. It works well for the first few generations, but after four or so generations, it starts to fall apart rapidly. What the methodology is doing for distant matching is really the opposite of what needs to be done.

How did this come about? The establishment missed a huge source of common ancestry within the last three hundred years, but it develop a methodology which skirts the results of that common ancestry.

Jack Wyatt
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  #5  
Old 19th October 2017, 11:19 PM
karwiso karwiso is offline
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Originally Posted by MMaddi View Post
There is zero chance of an NPE. The original poster shares over 3,000 cM with his father. This clearly indicates they are father and child.
Oh, sorry. You are right.
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  #6  
Old 19th October 2017, 11:58 PM
Frank Kelch Frank Kelch is offline
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Originally Posted by B198251 View Post
Hello,

I have hundreds of matches on Gedmatch. My father has hundreds matches on Gedmatch. I match my father with more than 3000 cM on Gedmatch. But we have only 1 (one!) common match on Gedmatch. How is this possible?
I don't think this is possible. Are you absolutely sure that you're reading the results correctly?
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  #7  
Old 20th October 2017, 03:28 AM
B198251 B198251 is offline
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Thumbs up

Hi,
Thanks to everybody for your answers.

I have found my mistake.
In "One to One" comparison tool the default threshold is 7cM match, but in "People who match one or both of 2 kits" the default is 10cM. That's why it showed me just one very strong match.
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  #8  
Old 20th October 2017, 10:33 PM
Frank Kelch Frank Kelch is offline
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Quote:
Originally Posted by B198251 View Post
Hi,
Thanks to everybody for your answers.

I have found my mistake.
In "One to One" comparison tool the default threshold is 7cM match, but in "People who match one or both of 2 kits" the default is 10cM. That's why it showed me just one very strong match.
I figured it was something like that... I'm glad you got it sorted out.
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