how do you determine a father/son relationship?

+3 votes
I submitted my dad's dna sample for evaluation.  Subsequently, we saw another sample show up with a genetic distance of 1.  That sample came from a man who was adopted and is searching for his biological father according to his profile.

Reading all I can about the definition of "genetic distance of 1" I have concluded this is not the method to find a father/son relationship.

How is this done?  I have a candidate for his biological father based upon our extended family history.  (It is not my dad.)
in The Tree House by
retagged by Lynda Crackett

1 Answer

+3 votes
The significance of a YDNA genetic distance of 1 depends, in part, on how many STRs were tested. If there was a GD of 1 between 2 111-STR marker tests, that suggests a possible close relationship. A GD of 1 between 2 12-STR marker rests is pretty meaningless. No YDNA test, however, will prove a father-son relationship. For that, you need an autosomal DNA test like 23 and Me or Family Tree DNA's Family Finder test. An autosomal DNA test should show that a parent and child share about 50% of their DNA. If they share close to 50% then it is virtually certain they are either parent-child or siblings.
by Chase Ashley G2G6 Pilot (203k points)

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