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Re: Family/Relative Finder - False Positives for those with Ashkenazi ancestors

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  • aj_levin
    Hi Dave, They ve made an adjustment to Relative Finder, I think around September, that was a slight improvement. Some of us have voiced our concerns even after
    Message 1 of 8 , Nov 23, 2010
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      Hi Dave,

      They've made an adjustment to Relative Finder, I think around September, that was a slight improvement. Some of us have voiced our concerns even after that, but my impression is their resources go foremost to the medical side.

      As of today 23andme is doing away with the ancestry-only edition and only selling the complete edition; as a plus they've added people who had had the medical-only version to Relative Finder, and people who had ancestry-only should now be able to download their raw data to run through aftermarket progrmans such as Promethease. If you haven't logged in for a while you might also want to check for more close cousins.

      Our block on chromosome 9 (120,000,000-140,000,000) is not shared with either my paternal grandfather or my mother, so the link should be through my paternal grandmother, so probably an Ashkenazi but possibly a Sephardi link. At 6 cM we definitely share an ancestor, but it's going to be too far back to trace. So far I have only had sucecss with blocks about 9 cM and larger, and preferably at least 11 cM.

      As for your non-linking to Rebekah: I also have some 7th-9th cousins who I have shared genomes with and we have no common DNA showing.

      What happens is your autosomes are inherited in blocks from different ancestors, and while you inherit roughly half your DNA from each parent and roughly a quarter from each grandparent, just a couple of generations earlier you may have inherited many of your genes from one ancestor and none from another. Third cousins will almost always show up, but somewhere around 4th and 5th cousins, it starts to fall off.

      By seventh cousins, there's a fair chance one (and quite possibly both) of you inherited no genes from that ancestor -- or they've been chopped up in recombination, so they're there but not recognizable. That's why it's always good to test the oldest generation available.

      On the other hand if you have inherited _any_ genes from an ancestor beyond about five generations, they may also have been passed down intact with little recombiantion for many generations. That's why a fully Ashkenazi person might see a 5.5 or 6.0 cM block with someone from Spain, say, with converso ancestry, or from Italy; it really does go back 500-600 years to a common Sephardi or Italqi ancestor!

      I hope this helps...

      A.J.

      --- In Ashkenazi-Q@yahoogroups.com, "Dave" <dshoward@...> wrote:
      >
      > AJ,
      >
      > Thanks so much for this great information.
      > Have you shared your comments with the 23andME people?
      > They always seem to be asking for feedback.
      >
      > I note that you and I share a 6 cM chunk on Chromosome 9.
      > However, that is it.
      >
      > Here is something interesting. Rebekah Canada is my 7th cousin on my mother's side. She and I share no segments.
      >
      > Dave
      >
    • Dave
      Very interesting. That you and your brother are slightly different makes sense. Every sperm and every egg have slightly different mixes of the chromosomes.
      Message 2 of 8 , Nov 23, 2010
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        Very interesting. That you and your brother are slightly different makes sense. Every sperm and every egg have slightly different mixes of the chromosomes.

        --- In Ashkenazi-Q@yahoogroups.com, "Bob" <Vick@...> wrote:
        >
        > Dave,
        >
        >
        >
        > Your results are interesting with many more declared Ashkenazi's than mine
        > below.
        >
        >
        >
        >
        > Ancestry
        >
        > Color
        >
        > Percent of Bob Vick's Genome Covered
        >
        >
        > Not declared Ashkenazi Jewish
        >
        >
        >
        > 49.3%
        >
        > -
        >
        > 50.3%
        >
        >
        > Declared Ashkenazi Jewish
        >
        >
        >
        > 0.2%
        >
        > -
        >
        > 1.2%
        >
        >
        >
        > These results are at maximum, including US & Canadian Ancestors which
        > brought up some X chromosome hits. When I use the 2 grandparents from the
        > same country the hits fall way back, with mostly Polish Ashkenazi
        > connections. I only know of Czech blood in my paper trail lines.
        >
        >
        >
        > I guess the point above could be that 50% of my ancestors forgot where they
        > came from, or likely never knew as their parents protected them from
        > histories realities.
        >
        >
        >
        > Cheers, Bob
        >
        >
        >
        > PS My brother has 87% of the same DNA that line up the same way as mine only
        > 56% of the time in segments. He matches people that I do not match, so it is
        > possible to have no segment alignment with some distant cousins, which a
        > sibling might match on.
        >
        >
        >
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