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Brothers with Slightly Different Ethnic Composition?

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  • Brothers with Slightly Different Ethnic Composition?

    Hi everybody,
    I have a question for the experts. I have received the ethnic composition of my DNA, and so did my older brother (same parents).

    Although the major elements are the same, there are a few variations that are quite frankly disconcerting, as they refer to completely different areas of the globe.

    Would it be an analysis error? Is there anything else going on?

    Thank you to all who will want to reply.

  • #2
    If you and your brother are shown with a relationship of "brother" to each other*, then having different amounts of mostly the same known ancestry is normal. Siblings share about 50% of their DNA with each other, but can inherit a different combination of DNA from their parents for the other 50%.

    What you describe as some variations from different areas of the globe I take to mean small percentages which FTDNA's algorithm found hard to place, and the algorithm misattributed ethnicities which seemed to match, but can be wrong. Are you saying that some of your population cluster percentages are from places that are not in your known ancestry? Are these small, such as < 1% or < 2% (which FTDNA calls "trace" results)?

    See some of these articles:Ethnicity Estimates (also called biogeographical or admixture estimates) are the least reliable aspect of testing DNA for genealogy. Your list of DNA matches is much more accurate than the ethnicity estimate you receive. See Roberta Estes' blog post, "Ethnicity is Just an Estimate – Yes, Really!" And the posts by Judy G. Russell, "The Legal Genealogist," also explain this:I suppose she can keep telling us the same thing for a long time to come. Estimating ethnicity is a hard thing to do with accuracy for all.

    *Full siblings share an average of 50% of DNA from their common parents, or a range from 32%-54%.


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    • #3
      im sorry but can this be right?
      same thing happened to me too with the results,how can it be that i have roots from x and my sister dont and she has roots from y and i dont?

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      • #4
        Originally posted by ER1992 View Post
        im sorry but can this be right?
        same thing happened to me too with the results,how can it be that i have roots from x and my sister dont and she has roots from y and i dont?
        ER1992: Did you read the first three bullets in my earlier post (#2)? They will explain why your sister and you might get different results in your ethnicity estimates. The other links from the second three bullets explain why ethnicity results are the least accurate part of testing DNA for genealogy.

        You seem to be confused about the types of DNA, and which ones are included in the Family Finder test at FTDNA (or the tests offered by 23andMe, Ancestry, and MyHeritage). There are four types of DNA (the links are to pages at ISOGG, the International Society of Genetic Genealogy):
        • Y-DNA, which only males have, passed down from fathers to sons.
        • mt-DNA (mitochondrial DNA), which both males and females have, but only females pass on to their children.
        • Autosomal DNA, which everyone has; it includes chromosomes 1-22, and is the type of DNA that the "Family Finder" test uses at FTDNA.
        • X-DNA is one of the sex chromosomes (along with Y-DNA), and is tested with the autosomal chromosomes, so is included with your Family Finder results; both males and females have X chromosomes.
        Here are some articles to explain all the above:You and your sister each get about 50% of your autosomal DNA from your parents, but this is inherited randomly. So, you may inherit some of the same DNA as your sister, but other parts will be different from your sister. That is why you may have some "roots" in your results that your sister does not, and she may have some that you do not. You and your sister will probably have different percentages of your ethnicities, and that is perfectly normal.

        For the two sex chromosomes, X and Y: while Y-DNA is only found on the paternal side, and only men have it, X-DNA cannot be used to represent only the maternal side; the inheritance pattern is more complicated, and includes some men (men have an X chromosome). But at Family Tree DNA (FTDNA), Y-DNA is not tested in the Family Finder test. Y-DNA test are offered separately.

        You and your sister did the Family Finder test, which includes only the autosomal chromosomes plus the X chromosome. You get your autosomal DNA from BOTH your mother AND father. X-DNA is tested as part of autosomal DNA, but has a different inheritance pattern than chromosomes 1-22: males get one X chromosome from their mothers, and one Y chromosome from their fathers; females get two X chromosomes, one each from their mother and father. See X-DNA’s helpful inheritance patterns byLouise Coakley for details.

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        • #5
          Originally posted by KATM View Post
          If you and your brother are shown with a relationship of "brother" to each other*, then having different amounts of mostly the same known ancestry is normal. Siblings share about 50% of their DNA with each other, but can inherit a different combination of DNA from their parents for the other 50%.

          What you describe as some variations from different areas of the globe I take to mean small percentages which FTDNA's algorithm found hard to place, and the algorithm misattributed ethnicities which seemed to match, but can be wrong. Are you saying that some of your population cluster percentages are from places that are not in your known ancestry? Are these small, such as < 1% or < 2% (which FTDNA calls "trace" results)?

          See some of these articles:Ethnicity Estimates (also called biogeographical or admixture estimates) are the least reliable aspect of testing DNA for genealogy. Your list of DNA matches is much more accurate than the ethnicity estimate you receive. See Roberta Estes' blog post, "Ethnicity is Just an Estimate – Yes, Really!" And the posts by Judy G. Russell, "The Legal Genealogist," also explain this:I suppose she can keep telling us the same thing for a long time to come. Estimating ethnicity is a hard thing to do with accuracy for all.

          *Full siblings share an average of 50% of DNA from their common parents, or a range from 32%-54%.

          Is this applicable also in twins? I'm just wondering because they were given birth at the same time thus, I'm thinking that they share exactly the same DNA.

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          • #6
            Identical twins are virtually identical in DNA. Fraternal twins are simply siblings who happen to have been born at the same time. Identical twins will show identical "ethnic origins", whatever that term means, while fraternal twins will probably differ, for the reasons already stated in this thread.

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            • #7
              True, identical twins should get identical ethnicity reports. A study was done in 2015, comparing 41 sets of identical twins at three major DNA testing companies: Ancestry, 23andMe, and MyHeritage, to see how closely their ethnicity percentages would match. This study was published in the American Journal of Medicine.

              The above study not only compared the twins at each company, but secondly, disregarding their twin status, they also compared each person's results from different companies. For twins tested at the same company, the results were found to be highly consistent between twins, with 23andMe being a bit lower. In contrast, individual results were not as consistent between companies. For the latter, the article linked above states:
              This is not entirely unexpected due to the nature of these algorithms which by design handles the highly complex genetic data in a way that does not produce 100% agreement for the same person.
              This illustrates, as we have heard for a long time, why ethnicity results are the weakest aspect of DNA testing for genealogy.

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