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When I trace an ancestor back, back and back, suddenly, my DNA link disappears, it's as if one of many greats grandparent misbehaved. I don't think Roger William was misbehaving, but my DNA disappears at that generation. Does DNA just get too spread out and leaves my genome?

For instance, on a genealogical site/service, I can trace my ancestry back to my 6th great grandfather. That gentleman's profile shows that we probably have DNA in common. The problem is that when I look at his father's profile, DNA tag is gone. Sometimes, I can get back to the 8th great grandfather and have the genetic linkage and sometimes the linkage and tag is gone in the 6th generation.

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    Welcome to G&FH SE! As a new user be sure to take the Tour to learn about our focussed Q&A format which is quite different from bulletin boards, discussion forums and other Q&A sites you may be used to. What type of DNA test have you undertaken? Was it AncestryDNA or something else?
    – PolyGeo ♦
    Sep 8, 2017 at 23:20
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    Please clarify what do you mean as "link disappears". There is the phemonenon that besides all your ancestors genealogically are your ancestor, but some of them are not ancestors in genetic terms. This happens because we don't get precisely 1/4 of DNA from our grandparents. So when we take a greater number of generations shared DNA with the particular great grand(several times) parents will be around zero
    – George Gaál
    Sep 9, 2017 at 9:07
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    This question isn't written clearly enough for us to give a good answer. The purpose of G&FH.SE is not just to answer your question, but for the answer to also help many other people who might have the same kind of question as you have. Telling us the name of one of your ancestors doesn't tell us where he is in your tree. If you tell us what relationship that person is to you, we will have a better idea of what is going on. Please use the edit link to add more information to your question.
    – Jan Murphy ♦
    Sep 9, 2017 at 20:45
  • @George Gaal. I believe you answered the question. For instance, on a genealogical site/service, I can trace my ancestry back to my 6th great grandfather. That gentleman's profile shows that we probably have DNA in common. The problem is that when I look at his father's profile, DNA tag is gone. Sometimes, I can get back to the 8th great grandfather and have the genetic linkage and sometimes the linkage and tag is gone in the 6th generation.
    – crazypieces
    Sep 9, 2017 at 23:50
  • Please use the edit button beneath your question to revise it with any additional information that would enable potential answerers to provide an actual answer.
    – PolyGeo ♦
    Sep 10, 2017 at 20:20

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Please clarify what do you mean as "link disappears". There is the phemonenon that besides all your ancestors genealogically are your ancestor, but some of them are not ancestors in genetic terms. This happens because we don't get precisely 1/4 of DNA from our grandparents. So when we take a greater number of generations shared DNA with the particular great grand(several times) parents will be around zero.

UPD: @crazypieces I am sorry I still don't precisely understand you :-) You said that you were able to trace the DNA back to "8th great grandfather". I believe that you, of course, didn't take the test from him, but you were able to confirm the relationship with another person with the DNA test and check out that you both have the same "8th great grandfather". It is OK.

But "The problem is that when I look at his father's profile, DNA tag is gone" is ANOTHER problem. It may mean different things. The first idea is that that this person has the match with you above some bunching limit. And his father - lower than this limit. It is usually 7cM in the FamilyTreeDNA service. It does not mean that you are not related with these persons. It just tells us about amount of shared DNA. Now you will ask how it may happened that the son has MORE shared DNA than father. There are many reasons:

  • the artifacts of matching algorithm, because it calculates half-matches. It sometimes gives false-positive results. I.e. in fact there are no such combination in your genes.
  • because there is shared DNA between you and the mother of this person. And in him both small segments from his father and mother were glued together, yielding longer segment (above the bunching limit)
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  • Thank you for that explanation. I found it useful. Please use a grammar checker. "you was able"?
    – crazypieces
    Sep 11, 2017 at 16:13
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    @crazypieces, yes, sorry and thanks for the correction. It is difficult for non-native to write English text on the phone
    – George Gaál
    Sep 11, 2017 at 17:18
  • @GeorgeGaál Kudos for trying. I am a native English speaker, and I sometimes have difficulty writing coherent English on a phone screen! ;)
    – sempaiscuba
    Sep 11, 2017 at 18:53

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