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Chromosome Browser

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  • Chromosome Browser

    Hi Folks,

    I have a question that I still can't find the answer to, after many years of research:

    When I put my mother into the Chromosome Browser, she matches me on all 22 base pairs and the X....literally almost every place that FTDNA tests.

    Why aren't there gaps there for what would be coming from my father's side?


  • #2
    There are no gaps for the DNA you got from your father, because both your parents gave you 50% of your total DNA. You got a set of your autosomal chromosomes (1-22 + the X chromosome) from each parent. The Chromosome Browser is correctly showing you the 50% that you share with your mother, which is one whole set of your autosomal chromosomes.

    The Chromosome Browser shows the #1-22 chromosomes, plus the X chromosomes, depicted as 23 dark (navy blue or black) bars; think of them as a "blank" background until you add any of your matches to view the matching segments.

    These bars stand for BOTH the maternal and paternal above chromosomes; therefore, you don't know from which side of your ancestors a match is linked, just by viewing the match in the Chromosome Browser (unless you already know the relationship, as in the case of your mother). There is no way for FTDNA (or any other genetic genealogy DNA testing company) to know if your match is paternal or maternal from the DNA, because they can't tell from which parent your matching markers come from. You might read Roberta Estes' post on "Nine Autosomal Tools at Family Tree DNA," where she describes the Chromosome Browser as tool #5. I'm sure she describes it better than I have.

    If your father had also done a Family Finder test, and you added him in the Chromosome Browser along with your mother, you would see that he matches you the same way as your mother (barring the X chromosome, if you are male - only females get one X from each parent).

    One way to determine if a match is paternal or maternal (outside of the Chromosome Browser):
    If you have any known relatives tested, and linked to your tree at FTDNA, then you can use the Family Finder – Family Matching Tool. Also in the FTDNA Learning Center, read more about the Family Matching System. You could create a tree, or upload a .ged file (GEDCOM), and then link your mother to her place in that tree.

    Roberta Estes also has two articles explaining the Family Matching Tool at FTDNA:
    Family Tree DNA Introduces Phased Family Finder Matches and Additional Relatives Added to Phased Family Matches at Family Tree DNA. If your father is not available to take a Family Finder test, you may have a paternal uncle or cousin, etc. who could test and thus, with your mother's test, help filter your match list into both maternal and paternal categories.
    Last edited by KATM; 4 July 2018, 06:44 PM.


    • #3
      We all have 46 single chromosomes, 23 pair

      We get 23 single chromosomes from ours mother's, each single chromosome is a random mixture of each of her pairs.

      Same applies to the 23 single chromosome's from our father, with the exception of his 23rd pair which is an X chromosome and a y chromosome. He passes entire X to daughters and entire y to sons.

      As mentioned, Chromosome browsers merge each pair into one due to fact the nature of testing can not say which is which.

      Each postion tested is given two values ,ie) AG, where one letter is value of that postion on maternal chromosome and the other letter it's corresponding position on paternal chromosome

      When you are matching someone, you are matching in what is half base pair matching or half identical. Meaning you are matching only on your maternal or paternal chromosome of the pair along that segment.

      Full siblings are generally the only ones that will match full base pair, or full identical. Meaning matching along the same section of their maternal and paternal chromosome
      Last edited by prairielad; 4 July 2018, 07:51 PM.