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  • Half Sibling might be full Sibling?

    My half-sister Dotty and I both did DNA tests through 23&Me. Our results are in and show that Dotty shares 58.4% of DNA with me. Below are the numbers that I received matching Dotty. We are so confused because years ago I was told that my A+ blood type would match either my mom or dad. Since our mom's blood type is B+, and Dotty and her Dad's are O+, we figured Dotty's dad could not be my dad. Our mom is getting ready to take the test too. Dotty's dad is deceased, so testing him is not an option.

    My questions are: (1) do you think these DNA results are showing us as full-sisters; and (2) is it possible that a male relative of Dotty's dad could be my father?

    Half identical
    2921 cM
    38 segments

    Completely identical
    1424 cM
    45 segments

  • #2
    Originally posted by Jam View Post
    My half-sister Dotty and I both did DNA tests through 23&Me. Our results are in and show that Dotty shares 58.4% of DNA with me. Below are the numbers that I received matching Dotty. We are so confused because years ago I was told that my A+ blood type would match either my mom or dad. Since our mom's blood type is B+, and Dotty and her Dad's are O+, we figured Dotty's dad could not be my dad. Our mom is getting ready to take the test too. Dotty's dad is deceased, so testing him is not an option.

    My questions are: (1) do you think these DNA results are showing us as full-sisters; and (2) is it possible that a male relative of Dotty's dad could be my father?

    Half identical
    2921 cM
    38 segments

    Completely identical
    1424 cM
    45 segments
    you are full siblings you have the same father and he probably has A blood type not O so good luck finding your dad

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    • #3
      Thanks

      Thanks for your guidance! There is no doubt that the man on my sister's birth certificate had a blood type of O+. He served in the military and his dog-tags show O+. Also, he went through surgeries and his doctor said his blood type was O+. So, based on your response, I am now thinking that maybe this man was not my sister's dad? I do know for a fact that my sister's blood type is O+, mine is A+ and our mom is B+.

      Thanks again for your information!

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      • #4
        Paternity_Blood_type_Chart-590.jpg

        here is a blood chart to help u

        Comment


        • #5
          Please read replies 59 and 62 here:

          http://www.rootschat.com/forum/index...opic=750462.54

          It explains that if you carry a certain gene your blood type shows as O when even though you have an A or B gene. Perhaps your father was A/O but had the inhibitor gene which meant his group appeared to be O.

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          • #6
            it doesnt work that way a O blood type is always o/o and a/o and o/a is always A blood type

            Comment


            • #7
              Stray second-hand mentions of an ABO "inhibitor" gene need to be far more specific. They MIGHT refer to the exceedingly rare "Bombay" blood type (you can Google this), in which certain ABO alleles (specific subtypes of both A and B) fail to agglutinate with anti-A and/or anti-B sera. It's a real thing, even if the number of known individuals who carry it is apparently only dozens out of hundreds of millions of people whose blood types have been tested.

              "Bombay" blood, however, still shows the same incompatibilities (depending on the underlying ABO genotype) as normal, non-"Bombay" blood. I don't know whether hospitals or blood banks routinely screen for this variant, or if so, when they began to do so in such a way that its presence would have been reported in patient records. If anyone has had a transfusion or organ transplant, I would think it is much more likely that the "Bombay" type would have been detected during the process of establishing compatibility prior to the procedure.

              For the present situation, the shared cM is at least as close as full siblings, unless there were an identical twin or something similar in the mix of parents. Comparisons with other relatives and careful attention to shared and non-shared segments should be followed up to be sure everything is consistent.

              Comment


              • #8
                I would say full sibling as well based on numbers.

                If you both are on gedmatch you can do one to one compare with graphic. If it shows large blocks of solid green then this strengthen full sibling as it is meaning you are marching along both your maternal and paternal chromosome's for those sections.

                As well if you are both female and you do X one to one you should match along the entire length of X if you share the same father, approximately 196cM. This is due to males having only one X which they pass on enact to all daughters

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                • #9
                  Can't thank you all enough!

                  My mom, my sister, my sister's dad, and myself have all had major surgery where our blood types were determined prior to surgery. The types never indicated anything other than the O+ (sister and her dad), B+ mother, and A+ for me. I gave blood for decades and the Blood service also shows mine as A+.

                  I've uploaded the DNA results for myself and my sister to GEDMatch. Below is our X Chromosome (mine is the first one)
                  B37 Start (me) 2,407,207 (sister) 62,150,601
                  B37 End (me) 58,488,110 (sister) 154,949,547
                  cM (me) 87.4 (sister) 105.1
                  SNPs (me) 4,087 (sister) 5,748
                  Largest segment = 105.1 cM
                  Total segments = 192.5 cM (98.239 Pct)
                  2 shared segments found for this comparison.


                  I began this DNA search to see if I could find out who my father is/was. I did the DNA test with my sister Dotty and another sister. My other sister's DNA kit didn't work and 23&Me is trying to test it again. Now, I am wondering if the brother of my sister's Dad could be my father. I must also consider that when we mailed in the kits there was a mix up on which vial # went with which sister. So, at this point I will wait until my other sisters results are done to explore further. Thank you to all of you for trying to help! This DNA stuff overwhelms me and getting advice is so appreciated!
                  Last edited by Jam; 1st August 2018, 11:02 PM.

                  Comment


                  • #10
                    3/4 sibling (share one parent, other parents siblings) maybe a possibility, but I think the total cM is a little high for that, possible.....3/4 siblings usually share between 1300 to 2300cM

                    On Average
                    Full siblings 2550 cMs
                    Three quarter siblings 2125 cMs
                    Half-siblings 1700 cMs

                    Note if cM amounts are from 23andme, one must remove the X amount shared. X amount is not used in determining relationship ranges in cM totals, only chromosome 1 thru 22 are used.

                    So for example, your 2921cM if from 23andme, would be 2921cM - Total X amount shared. That is the total you would use when referencing charts.
                    What does Gedmatch give as total cM shared between you when you run the One to One Autosomal Comparison?
                    Last edited by prairielad; 1st August 2018, 11:38 PM.

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                    • #11
                      I would sit down and have a long conversation with your mom and hopefully she will confess who your father really is

                      Comment


                      • #12
                        Originally posted by Jam View Post
                        I am wondering if the brother of my sister's Dad could be my father. I must also consider that when we mailed in the kits there was a mix up on which vial # went with which sister.
                        There is too much DNA shared between the two kits to share the same mother and be fathered by brothers unless the brothers were identical twins. You mention there is another sister who is in the process of having her DNA analyzed. Is she a full sister to your other sister and what is her blood type? If you think you might have mixed up the kits that is really unfortunate. It would be difficult for anybody to help you until you get that straightened out. You might end up needing to test yourself again which might help you in the long run anyways by either testing yourself here at FTDNA or at Ancestry. Maybe just waiting on the other kit's DNA results will shed more light on all of this.

                        Comment


                        • #13
                          There's also the possibility that parents were related to each other! At least that possibility can be tested on GEDmatch, there's a tool for that. In order for this possibility to seriously distort the results reported in this thread, the relationship of the parents to each other would have to be rather close, and thus easily detectable by the "Are your parents related" tool on GEDmatch.

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                          • #14
                            Originally posted by John McCoy View Post
                            There's also the possibility that parents were related to each other! At least that possibility can be tested on GEDmatch, there's a tool for that. In order for this possibility to seriously distort the results reported in this thread, the relationship of the parents to each other would have to be rather close, and thus easily detectable by the "Are your parents related" tool on GEDmatch.
                            At the level of DNA shared here (58%) your scenario would be incest. I doubt very much that is the case here.

                            Comment


                            • #15
                              When there are questions and possible confusion, the tools at GEDmatch are strongly recommended. It may be possible to get a slightly clearer view of the possible scenarios and rule out some of them. Among other options that are available, the "Are my parents related?" tool, the One-to-One comparison tool with graphics option (so that you can spot, and to some extent measure "Fully-Identical Regions" that are not shown or counted at FTDNA), as well as the ability to compare any kit with any other kit in all combinations. GEDmatch is free, the tools are easy to use.

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