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  • How much DNA?

    I decided to find out how much DNA we get from our greatgreatgrandparents,etc. So I made a little "chart."
    The further back you go, the less DNA you inherit. I'm only listing up to about 1%. The list goes further.

    Who - How many do you have - What percentage of DNA do you inherit

    Self - 1 - 100%
    Parents - 2 - 50%
    Grandparents - 4 - 25%
    GreatGrandparents - 8 - 12.5%
    2nd GGP - 16 - 6.25%
    3rd GGP - 32 - 3.125%
    4th GGP - 64 - 1.5625%

  • #2
    Your computation only applies to autosomal DNA and then, the pattern of inheritance may not be strictly 50/50. Could be an average of 50/50 over a wider sample. Certainly 50/50 for autosomal STR's. Probably not 50/50 for autosomal SNP's. Depends on what you test and who you test with. Admixture, of some sorts, creates linkage disequilibrium in the autosome.

    We get our Y and Mt DNA pretty much 100%, pretty much 1-to-1, from our respective parents.
    Last edited by tomcat; 11 March 2007, 07:43 PM.

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    • #3
      Yes I meant autosomal. Not mtDNA or yDNA.

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      • #4
        Originally posted by tomcat
        Probably not 50/50 for autosomal SNP's.
        Why? What make the herritance different between STR and SNP?

        Noaide

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        • #5
          'Cause DNAP, that tests autosomal SNP's, will not stand behind 50/50 inheritance. 'Cause SMGF is running autosomal tests predicated on presence of autosomal L-D. 'Cause entire paternity/identity industry is predicated on Mendelian inheritance of atSTR's.

          When you make money or published studies in DNA, maybe I will believe you
          Last edited by tomcat; 11 March 2007, 09:12 PM.

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          • #6
            How far back does DNA go?

            Something has been bothering me for awhile. I took the AncestrybyDNA test. It tells you what percentage you are of the 4 biographical groups. My result was 90% European and 10% Native American(My range can go as high as 18-20%) 10% or greater (which I have)is considered fairly accurate. I have verified heritage to the Potowomecke of Stafford and King George Cty,VA through Rev. John Waugh. This goes back to 1600's. I am in contact with the tribal historian Bill Deyo. We are off of the same ancestor, Wahangonoche. If the 10% is not from my verifed tribe(since it isn't suppose to go back that far, or does it?) what other tribe(s) do I belong to? Somebody must be keeping a secret somewhere. How far back will it realistically go. If the 10% isnt from the 1600's, what generation are we talking about. Great grandparents?
            Maria

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            • #7
              Originally posted by Maria_W
              If the 10% is not from my verifed tribe(since it isn't suppose to go back that far, or does it?) what other tribe(s) do I belong to? Somebody must be keeping a secret somewhere. How far back will it realistically go. If the 10% isnt from the 1600's, what generation are we talking about. Great grandparents?
              Maria
              I think if the 10% is indicative about something real native american ancestry, and no more recent geneology shows any native american influence there must be more native than the native americans you have found who has native american blood among your anchestors. Maybe from the time of the earliest pioneers if your geneology go that far back that married native americans females. These native american genes have since then been spread among a few percentages of todays modern US population and appear as a native american "static" in your and many other americans test result.

              Noaide

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              • #8
                Originally posted by Noaide
                Why? What make the herritance different between STR and SNP?
                There is no difference. Autosomes are inherited 50/50 from each parent under normal circumstances, and both SNPs and STRs are along for the ride just the same.

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                • #9
                  Originally posted by Maria_W
                  If the 10% is not from my verifed tribe(since it isn't suppose to go back that far, or does it?) what other tribe(s) do I belong to? Somebody must be keeping a secret somewhere. How far back will it realistically go. If the 10% isnt from the 1600's, what generation are we talking about. Great grandparents?
                  First, these tests are not perfect at separating Asian from Native American backgrounds.

                  The results are clearly suggesting that Wahangonoche is not your only Native American or Asian ancestor.

                  The most probably scenario is that your 10% Native American result is an aggregate of several factors: some recent known Native American ancestry (Wahangonoche?), some other recent unknown Native American ancestry, and some background levels of ancient Asian admixture in your European ancestors.

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                  • #10
                    Native heritage hiding!

                    Well I do know that I have the heritage from at least one tribe. Even the tribal historian mentioned having more lines then I knew about. Maybe I should look into it more. I do have some missing female spouses, some with no last name out of VA, DE, MN, MA, PA, NC, NJ, etc.I saw on the website and was also told by the people at AncestrybyDNA that if your results are 10%(which I have) or greater in the Native category than the chances are pretty high, I think 95%, that you do have a true affilation with that group. I ask them if Native could be confused with Asian. They were very insistent that Asian markers are totally different and that I did not have Asian ancestry. Which I wound not have any issue with if I was Asian! Also they said that people who come up with Asian markers are usually Asian and not Native. Go figure! Have seen one poor man with 60% Native heritage and was tested at 100% European. Didn't know what his claim was based on, didn't personally know him. He was very upset! Thats the worst example I have seen so far. For me it seems to be fairly accurate. Now I just have to start to find these other ancestors.

                    Maria

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                    • #11
                      Originally posted by Maria_W
                      ...
                      If the 10% is not from my verifed tribe(since it isn't suppose to go back that far, or does it?) what other tribe(s) do I belong to? Somebody must be keeping a secret somewhere. How far back will it realistically go. If the 10% isnt from the 1600's, what generation are we talking about. Great grandparents?...
                      Maria
                      If the inheritance is always 50/50, and you had just one Native ancestor in the 17c your AbDNA reading must be an error. If inheritance is not 50/50 and you had just one Native ancestor in the 17c your reading might be correctly reading that ancestor. If you had additional unknown Native ancestors then anything is possible.

                      This much is certain: Linkage disequilibrium has been seen throughout the autosome. Certain types of admixture create linkage disequilibrium. Hence some of those AbDNA SNP's could be in linkage disequilibrium and inheritance is not strictly Mendelian, not strictly 50/50.

                      The STR's are unlinked and inheritance is always strictly Mendelian. That is why they are employed for paternity tests and forensics.

                      I got 31% NA on AbDNA. My mother was C1 and looked Native. Her children also look Native. My father was the son of a pair of Ukrainian Jews, Ashkenazim. Some Ashkenazim have also pulled NA on AbDNA. So I can't say whether my 31% came from my father or mother, or both. There is a good reason to think that if both, it was not 50/50. Hence, I can't say whether my 31% NA is a true reading of my mother's 62% NA (supposed under the 50/50 rule).

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                      • #12
                        No doubt.

                        Tom.
                        Well, I have absolutely no doubt about the Powomecke heritage but... if that is not where the 10% comes in, then, I have alot of research to do to see where the other lines come in. If I got 10% and you got 31%(these aren't exactly even numbers, like 100, 50, 25, 12.5%, 6.25, ect.)doesn't that show that it isn't being given to us in equal amounts or is everyones test results who gets an uneven number wrong? I am just going to test my parents and see what they come up with. By the way both parents are from the same ancestor, Wahangonoche, he had at least 2 daugthers, my father is a decendent of Keziah/Arroyah and my mother decends from Mary(do not know Native American name, this is Christain name)
                        Maria

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                        • #13
                          I think that it is very clear that we need more multi-generational testing to make sense of autosomal results.

                          John

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                          • #14
                            Human Evolutionary Genetics, Origins, Peoples & Disease. Jobling, Hurles and Tyler-Smith. 2004 Garland.

                            Page 388. 12.5.1 How does admixture generate linkage disequilibrium?

                            In Chapters 3 and 5 we encountered the phenomenon of linkage disequilibrium (LD), whereby two alleles at different loci tend to be co-inherited more often than we might expect. In theory, admixture events should generate LD between all loci at which differences in allele frequency exist between the two ancestral populations (...). However LD between unlinked loci (self-contradictory though this may sound) dissipates rapidly over a few generations as a result of chromosomal segregation. LD at physically linked loci decays more slowly due to recombination events. As a result, recently admixed populations should exhibit LD over greater genetic distances than non-admixed populations. ...

                            A number of factors affect the extent of LD exhibited by an admixed population. These include:
                            the time since admixture;
                            the admixture dynamics, e.g. instantaneous or continuous gene flow;
                            the relative contributions of different ancestral populations;
                            the allele frequency differences between ancestral populations;
                            the pattern of recombination in the human genome.

                            The presence of longer than expected lengths of LD represents an opportunity to identify 'cryptic' admixture events, for which historical evidence is lacking or contentious. These theoretical predictions about the relationship between D and admixture have been backed up by computer simulations (...). However, very little is known about the pattern of recombination in the human genome, and so it is of interest to see if empirical evidence can be found for extended LD in admixed populations. One confounding factor is that length of detectable LD appears to be highly variable between different parts of the genome, making comparison between different loci impossible.

                            (Also see this thread in this forum and follow link to the SMGF paper - Linked autosomal STR haploblocks in SMGF comming autosomal database?)

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                            • #15
                              DNA for dummies!

                              Tom.
                              Could you break it down for those of us who are dna challenged (genetics for dummies). Maybe I am just tired but it is way over my head!
                              Maria

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