Ancestry V1 vs V2 – Shared DNA and Relationship Predictions

I reviewed the results of Ancestry’s V1 chip in comparison with their V2 chip relative to matches recently in the article titled Ancestry V1 vs V2 Test Comparison.

I had previously tested on the V1 chip, and recently tested on the V2 chip to see how many of the same matches were present on both match lists. The results were better than expected. Out of my 333 V1 Shared Ancestor Hint matches, all but 7 were on the V2 match list. Given that Ancestry replaced almost half of the SNPs on their chip, that’s an amazingly high retained match number – about 97.5%.

Another genetic genealogist asked about how much of the DNA is the same, or in common for the individual matches. In other words, did the amount of shared DNA with individual matches change between the two chip versions?

While Ancestry does not provide us with a chromosome browser, they do provide us with the amount of DNA in common with a match after their Timber algorithm removes segments that Ancestry feels are “too matchy.”  You can read more about how this is done, here.

ancestry-self-to-self-shared-dna

In the screen shot above, you can see that the amount of shared DNA is displayed when you click on the “i” button beside the confidence level of the predicted relationship.  In this case, I’ve looked at my V1 kit match to my V2 kit match.  Clearly, I don’t have 26 chromosomes, so some of my chromosome segments have been severed, either by faulty reads or by Timber removing segments.

Because of Timber, the amount of shared DNA shown by Ancestry is not the actual amount of matching DNA when compared to matching DNA at any other vendor or Gedmatch.  However, the amounts of shared DNA are consistently calculated between the V1 and V2 chips, so comparing Ancestry V1 to Ancestry V2 is certainly reasonable.  What we don’t know is whether this is the same DNA that is matching between V1 and V2, or if the matching DNA is actually on different segments, partial segments or different combinations of segments.  Without a chromosome browser or specific segment information, we have no way of knowing or discovering that information.

In the chart below, I’ve compared my 100 top shared ancestor hint (green leaf) matches (other than my own V1 to V2 kit comparison), meaning those with tree leaf hints indicating:

  • That our DNA matches and
  • That we share at least one common ancestor in our trees

Please note, for purposes of clarity, a shared ancestor hint (green leaf) does NOT mean or confirm that the DNA we share is from that common ancestor. The shared DNA could be from a secondary or different common line or the genealogy could be incorrect in one or both trees.  The fact that we share DNA, and that we have an identified common ancestor in our trees are independent pieces of information that both serve as important hints.  Both need to be verified.  Without a chromosome browser and triangulation, we cannot confirm that the shared DNA is from that particular ancestor.

Amount of Shared DNA Between V1 and V2 Chips

For each of my 100 top V1/V2 shared ancestor hint matches, I recorded the amount of shared DNA as displayed by Ancestry and the number of shared segments.  In addition, I also recorded the Ancestry predicted relationships and actual relationships as shown in my tree and my matches tree, as shown in the example below for Match 1.

ancestry-common-ancestors

My top 100 matches are shown in the table below, with their V1 and V2 results along with predicted and actual relationships.

  • Bold=increases and decreases in the amount of shared DNA
  • Red=increase or decrease of 2cM or greater
  • Yellow=increase or decreases in the number of shared segments

ancestry-shared-cm-and-rel

Increases and Decreases

Of the various matches, 9 increased between V1 and V2, indicating that these individuals match on some of new newly included SNPs.

On the other hand, 52 decreased between V1 and V2 indicating that some of the SNPs where they previously matched have been removed on the new (current) chip.

Increases and decreases are bolded, including those in red which signify an increase or decrease of 2cM or greater. Nine matches had an increase or decrease of 2cM or more. Of those, 2 increased and 7 decreased.

The maximum increase was 5.3 cM.

The maximum decrease was 6 cM.

In most cases, the number of shared segments remained the same. Of the 4 that changed, 3 decreased and one increased, indicated by cells highlighted in yellow. In one case, the cMs dropped, but the segments increased, causing me to wonder if a segment was split in the V2 version. In another instance, the shared cMs remained the same, but the segments moved from 2 to 1. I’m not sure how to explain that one, except for the possibility that some of the removed SNPs caused the measured area to be counted as one instead of two, or perhaps the matching segments aren’t the same.

Actual vs Predicted Relationships

Eight people, or 8% had private trees meaning they can see the identity of our common ancestor, because my tree is public, but I cannot see the identity of that ancestor.  That also means that I can’t determine the actual relationship for this comparison.

The 5 noted with ? means the ancestor is not the same ancestor or the match’s tree information is incorrect.  In this case, that means 5% of the tree matches, or common ancestors as indicated in the trees are known to be inaccurate for one reason or another.  There are likely additional inaccurate “common ancestors” given the amount of “tree grafting” that occurs.

In two cases the relationship was further out in time than predicted, although the predicted ranges are fairly broad and do significantly overlap. For example, one range is 4-6th cousins, and the next range is 5-8th cousins.

In 16 cases the relationship was closer than predicted.

I do have an endogamous Acadian line as noted.

In all cases, the amount of shared DNA was within the range of other people whose predictions were accurate, so this prediction variance is clearly a factor of the variability of inheritance of DNA.

The Net-Net

The net-net of this exercise is that when comparing the shared DNA between the same match on the V1 and V2 chip, far more people lost matching DNA than gained – 52% vs 9%.  In this comparison, all 100 of the people remained as matches, which isn’t surprising since these are my 100 closest shared ancestor hint matches, meaning those with the highest amounts of shared DNA.  However, with matches that have “less to lose,” meaning more distant matches having fewer matching centiMorgans of DNA to begin with, matches are more likely to be lost.

In this comparison, the people who appeared as matches on the V1 chip remain as matches on the V2 chip, but just over half showed less matching DNA utilizing the V2 chip.

20 thoughts on “Ancestry V1 vs V2 – Shared DNA and Relationship Predictions

  1. Question, I have purchased Ancestry kits in the past (before V1-V2) change. They have been sitting on my shelf waiting to be used. Will they be processed by the NEW V2 chip? Thanks. Karen

  2. Hi Roberta. The only thing I would add to your article is that of the two tests, I’m picking up significantly more new matches daily on the V2 chip. I’m really glad I did the second test.

      • Is this suggesting that those of us on V1 should retest with V2 to ensure getting new matches? Aren’t V2 tests still being compared to V1 tests? Why would there be a difference in rate? Or is this only applicable at the more distant matches?

  3. Ancestry has not been giving me shared cMs for about 2 months. There is some idiotic relationship list. It makes the testing I did totally lacking in utility.

  4. I had thought that your previous comparison of V1 vs V2 had some relevance to the question as to when FTDNA will once again accept transfers from AncestryDNA, since the results were so comparable. However when I asked a FTDNA representative about this at the recent i4gg conference, she said that the difficulty was that with the V2 chip they were getting something like 50% no calls which was not acceptable. She did not have an estimate on when they might accept transfers again. I have 2 kits that I would like to transfer, but it seems that I might have a long wait.

  5. “In the screen shot above, you can see that the amount of shared DNA is displayed when you click on the “i” button beside the confidence level of the predicted relationship. In this case, I’ve looked at my V1 kit match to my V2 kit match. Clearly, I don’t have 26 chromosomes, so some of my chromosome segments have been severed, either by faulty reads or by Timber removing segments.”

    Yeah right. Just admit it, the truth is finally out. You are a member of a 26 chromosome sister species of lizard people that comes from another star and is secretly bent on world domination. The genetics gig is just a cover to allow you to locate your fellow agents. The Cubs winning the World Series was actually a secret message telling your teammates that it is almost time to make your move. Both of the Presidential candidates are lizard person agents. If they weren’t wouldn’t they have publicly released their Ancestry reports?

    Anyway, have a nice day. It’s always a pleasure to read your posts.

  6. And, shared DNA with your match could be shared with an ancestor NOT in either of your trees, because it is behind a blank wall, and perhaps never to be discovered, unless you do triangulation with others in which case, it might prove a certain ancestor SHOULD be in your tree.

  7. I cannot believe that anyone would chase 15,18,20,3x,CM in the 1st place if your like me you likely have hundreds if not thousands of these ? The Autosomal is so hard to get any accurate handle on in the first place! I have attended 3 seminars and everyone had a different “HOW YOU DETERMINE” theory. If it isn’t a 2nd cousin 50 or higher they can delete them for all I care! TILL Ancestry.Com or FTDNA comes up with a more ACCURATE or AUTOMATED way to work with AUTOSOMAL its more trouble than its worth to flaky!

  8. I have both v1 and v2 results for myself, and v2 results for my wife and daughter. I show up in my match list for either of my kits as “self/twin”, with “3,489 centimorgans shared across 25 DNA segments”. Of course that *ought* to be a mere 23 segments, since clearly I must share all of my 23 pairs of chromosomes with myself. If the X chromosome is not included, then it should only be 22.

    How much I share with my daughter depends — slightly — on whether I’m looking at my v1 results, or my v2 results. If it’s v1, we have “3,453 centimorgans shared across 54 DNA segments”; if it’s v2, we have “3,468 centimorgans shared across 54 DNA segments”.

    These are actually extremely close results. It’s only the “Timber” issue that’s troubling to me, because obviously I don’t share 54 segments with my daughter. It ought to be less than half that number.

  9. Pingback: 2016 Genetic Genealogy Retrospective | DNAeXplained – Genetic Genealogy

  10. Some of my matches who have brought over their kits from Ancestry to FTDNA are not showing X match where we would expect. For example, a 2nd 1X cousin from my half aunt, (I share X with both) does not X match my aunt, but the daughter of the 2nd 1X does X match my aunt. How could her daughter match and not her mother? However the mother recombines, it should show up if the daughter is matching. We know where we tie together and the X should be there. The mother’s kit was brought over recently from Ancestry, the daughter’s some years ago.
    Another match to my aunt, other side of her family, has only 4 x matches out of 300, the first ten or so pages of matches.

    Any insight on Ancestry to FTDNA that could be affecting this? Both seem open to the idea of doing another test directly from FTDNA to resolve the questions.

    Thanks for your excellent, fun blog Roberta. You have encouraged me to delve into DNA genealogy and it has paid off (with a lot of hard work).

    Cheers!

    • Remember, a child can inherit a chromosome in whole from one parent, meaning they get all of one grandparent’s DNA and none of the other’s on that chromosome. That could be the case. The ancestry kits I’m assuming are both V1 from Ancestry of they could not be imported, so the version should not be the problem. I can’t really follow the logic with the Xs above. If you want a Quick Consult, I would be glad to do one for you.

      • Yes, it isn’t logical. Sorry if my writing is not clear. The children are matching to my aunt, but their mothers aren’t: it is skipping a generation. I’ve just found yet another female match, who imported her kit from 23andMe, who does not x match my aunt, but her daughter does x match my aunt. I match both the mother and the daughter on the X.
        I match my aunt at about 118 cM on the X.

        Thank you for the link. I may be contacting you in the near future for a more in depth review of other questions. I will try to resolve this with FTDNA.

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