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  • Father-Daughter FF differences

    I manage kits for myself and my deceased father. He has 1694 matches. Running the ICW tool shows only 649 of those matches to be in common with me. Shall I assume that all 1694 matches are really related to me, but do to the matching segments in my kit being below some threshold, they are not showing up in my list?

  • #2
    Originally posted by LHolt-Galvin View Post
    I manage kits for myself and my deceased father. He has 1694 matches. Running the ICW tool shows only 649 of those matches to be in common with me. Shall I assume that all 1694 matches are really related to me, but do to the matching segments in my kit being below some threshold, they are not showing up in my list?
    You do understand that you only received 50% of his DNA, don't you ? So it's normal that you don't have all the same matches.

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    • #3
      Originally posted by Parameswara View Post
      You do understand that you only received 50% of his DNA, don't you ? So it's normal that you don't have all the same matches.
      Of course I know that. I expect to see many people in my kit who do not match my father. What I was asking is when I am on HIS kit page, why does HE have 1045 matches that do not match me?

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      • #4
        why does HE have 1045 matches that do not match me?
        Because about half of the segments your father has didn't get passed down to you! Most of those 1045 matches are on the segments you don't have.

        Your dad has two chromosomes numbered 20, for example, but was able to only give you HALF of that genetic material. One side of your chromosome 20 comes from pieces from your dad while the other side comes from pieces from your mom.

        Also because there are times when FTDNA's matching criteria (20 cM total autosomal DNA shared and 7.69 cM minimum for at least one segment) aren't satisfied by both a parent and a child even when a segment may be contained in both the parent and the child. So only the parent, in some cases, will show enough DNA matching the match, but in GEDmatch it can be seen that the child also has some DNA on that segment, but (usually) less because the segment can break down into a smaller size in a child.

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        • #5
          Originally posted by LHolt-Galvin View Post
          What I was asking is when I am on HIS kit page, why does HE have 1045 matches that do not match me?
          Because of the other half of HIS genome you did not inherit. Also, because some of the segments you did inherit from him were recombined even further than they were in your father's chromosomes. Simply put, you are one generation further away from your father's matches than he is.

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          • #6
            Thanks. That makes sense.

            I still have a question related to this topic.

            I match two to women (mother and daughter) who on paper can be traced to a common ancestor on my paternal line about 8 generations back, but they do not match my father. Incidentally, they both are X-matches to me. Should I consider that they are actually matching to an unknown person on my maternal line and not to my paternal line?

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            • #7
              Originally posted by LHolt-Galvin View Post
              Of course I know that. I expect to see many people in my kit who do not match my father. What I was asking is when I am on HIS kit page, why does HE have 1045 matches that do not match me?
              Some of these will be matching him on the 50% of his DNA that you did not receive.

              But some of these matches will also not match you even though you may have the same longest segment present in your DNA due to you not have the 20cM total shared DNA to be declared a match by FTDNA.

              To be declared a match requires a longest segment of at least 7cM/500SNPs and a total shared DNA of at least 20cM.

              They will most likely be the ones that share 20 to 30 cM with your father and only have one segment between 7 to 19cM

              If you and these matches utilize Gedmatch, you can compare using the one to one compare and see if these longest segments that are shared show up between you and these matches.

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              • #8
                Originally posted by LHolt-Galvin View Post
                Thanks. That makes sense.

                I still have a question related to this topic.

                I match two to women (mother and daughter) who on paper can be traced to a common ancestor on my paternal line about 8 generations back, but they do not match my father. Incidentally, they both are X-matches to me. Should I consider that they are actually matching to an unknown person on my maternal line and not to my paternal line?
                What is the cM and SNP size of the longest segment?
                What is the total cM shared?
                What is the cM and SNP size on X?

                If you use GEdmatch, you can phase your results with your father which results in a Maternal and a paternal file for you.
                If matches utilize Gedmatch also, you can compare both these files to theirs using the one to one compare and see which file shows the match.

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                • #9
                  Originally posted by prairielad View Post
                  If you use GEdmatch, you can phase your results with your father which results in a Maternal and a paternal file for you.
                  If matches utilize Gedmatch also, you can compare both these files to theirs using the one to one compare and see which file shows the match.
                  I have our kits on GEDmatch and did try to phase without my mother's DNA since she is deceased. I'm not sure how to use the tools, but will go there and try again and see if I can learn more about how to do this.

                  Thanks

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                  • #10
                    Originally posted by LHolt-Galvin View Post
                    Thanks. That makes sense.

                    I still have a question related to this topic.

                    I match two to women (mother and daughter) who on paper can be traced to a common ancestor on my paternal line about 8 generations back, but they do not match my father. Incidentally, they both are X-matches to me. Should I consider that they are actually matching to an unknown person on my maternal line and not to my paternal line?
                    I agree this is odd. Having all the folks in one db (like GedMatch or here) and using a chromosome browser could show where/why this might be. That far back suggests cousin marriage/pedigree collapse, based on my own experiences. Key would be segments where these 'paternal side' paper ancestors match you but not your dad. Can you post a screen shot of the mother/daughter to you, or send via PM?

                    Are your dad and the 2 women on GedMatch? [can do chromosome compare on them there...]

                    Any of your mom's siblings available to test?
                    Last edited by hansonrf; 22 January 2016, 12:03 AM. Reason: completeness

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                    • #11
                      Originally posted by LHolt-Galvin View Post
                      I match two to women (mother and daughter) who on paper can be traced to a common ancestor on my paternal line about 8 generations back, but they do not match my father.
                      For a random pair of currently living people descending from a single ancestor couple 8 generations ago it is quite normal that they do not match in FF, because they really do not have enough shared DNA segments, or the largest shared segment (in cM) is too small.

                      Originally posted by LHolt-Galvin
                      Incidentally, they both are X-matches to me. Should I consider that they are actually matching to an unknown person on my maternal line and not to my paternal line?
                      As a woman, you have inherited your father's single X chromosome as such (except the new mutations), and the other of your X chromosomes recombined from your mothers two X chromosomes.

                      Both you and the matching mother and daughter descend from an unknown person on your maternal *side* (including your maternal line which, however, is the worst guess theoretically) via X inheritance allowing (that is, no two males in succession) lineages.

                      Nothing in theory prevents you to be related the matching mother and daughter via the paper lines, and via the unknown X inheritance lines, and still via some other autosomal DNA retained lines.

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                      • #12
                        Thanks.

                        I'm leaning towards multiple lines of descent on my father's line as a possible explanation. The woman's son does show up as a match to my father on 2 chromosomes.

                        On GEDMATCH a 1:1 compare shows the following:
                        to the mother on chrome 10 at 10.4 cM
                        to the daughter on chrome 10 at 10.4 cM
                        to the son on chrome 10 at 10.4 and chrome 16 at 5.5cM.

                        FTDNA is only reporting a match to the son on my dad's page.
                        Both women match me at 4cM on the X gene and all three of the above people are listed as matching me on my page.

                        I guess that the women are missing some threshold cutoff for being considered matches to my dad, but because the son has the additional match on chrome 16, he is considered a match.

                        This is all very confusing to me.

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                        • #13
                          I can't figure out how to post a screenshot.

                          I'm leaning towards your suggestion of pedigree collapse as the explanation. See my previous posting.

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                          • #14
                            Where I have personally seen this before is in cases where there were multiple common ancestors back as far as 8 generations in colonial New England. I have seen one instance personally where Askenazi roots presented as many small segments (upwards of 30) in the 3-7 cM range falling under the discriminators used at FTDNA or 23andMe, whatever they may be.

                            What only FTDNA can answer is why they don't show a match to your dad on chromo 10. I would compare on DNA.land if you can get all the kits uploaded.

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