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Thread: Reference populations for AncestryDNA

  1. #11
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    Quote Originally Posted by Nqp15hhu View Post
    So there is a limited reference population for Scotland? Interesting.
    It looks like none of their references actually come from Scotland, if some do they're from the Southeast
    Paper trail ancestry to the best of my knowledge:
    English 28.12%, German 18.75%, Scottish 17.96%, Irish (mostly lowland Scottish origin) 12.5%, French 8.2%, Eastern European 6.25%, Welsh 3.125%, Native American 1.95%, and Colonial American, 3.125%, which cannot be determined with complete certainty: there is Dutch (at least 1.36%) and some English. The rest could include Spanish, Norwegian, German, French, and Native American, but these percentages would be minuscule.

  2. #12
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    Quote Originally Posted by sktibo View Post
    It looks like none of their references actually come from Scotland, if some do they're from the Southeast
    didn't the northeast coast of Scotland have significant Scandinavian influences, and wouldn't that omition skew the population sample? same for Italy's heel and the Balkan/Albanian influences?

  3. #13
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    I didn't realise their sample was so small. I had thought it was pretty large as it did come out recently that they had several million samples, but I guess that isn't the same as a Reference Population.

    Does this mean the Ancestry results aren't reliable?

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    Quote Originally Posted by JerryS. View Post
    didn't the northeast coast of Scotland have significant Scandinavian influences, and wouldn't that omition skew the population sample? same for Italy's heel and the Balkan/Albanian influences?
    Well Orkney and Shetland have the largest Scandinavian influence, the average on the POBI Orcadian regions comes out to 26.83%. The Northwestern Islands of Scotland appear to have the second largest amount of Scandinavian influence - POBI's NW Scotland has an average of 21.5%. I imagine the Isle of Lewis would have more of this, there were three Lewis samples off the top of my head but most of the samples for this region were actually from Argyll and Islay. The Northeast, Aberdeenshire area, has less Scandinavian than this at an average of 16.1%.
    So I suppose the Northeast coast of Scotland doesn't actually have that much Scandinavian influence compared to the Northwest coast and the Northern Isles / the Northern tip. The Western Isles / Hebrides along with the Northern Isles were the primary areas of Scandinavian influence in Scotland, so I suppose this makes sense historically speaking. I have no idea about Italy
    Paper trail ancestry to the best of my knowledge:
    English 28.12%, German 18.75%, Scottish 17.96%, Irish (mostly lowland Scottish origin) 12.5%, French 8.2%, Eastern European 6.25%, Welsh 3.125%, Native American 1.95%, and Colonial American, 3.125%, which cannot be determined with complete certainty: there is Dutch (at least 1.36%) and some English. The rest could include Spanish, Norwegian, German, French, and Native American, but these percentages would be minuscule.

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    Quote Originally Posted by sktibo View Post
    Attachment 12078

    I had given up on trying to find out where their population samples come from, until I came across this little image...

    Does anyone have a larger version?

    Thank you
    It seems odd that they label France in the Europe West category when 2/3 of the country is lacking reference samples. It also explains why people in the southern half of France are getting such inflated Iberian scores.

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    Does anyone know how exactly a customer's DNA is compared to the reference panel? I've read the ethnicity white paper, but I still don't fully understand the details.

    For example, the Caucasus region includes 58 samples (although we don't how many samples were taken from each country in the defined region, or whether at least one sample was taken from each country). Is each customer's DNA compared to each of the 58 individual samples from the Caucasus, or does AncestryDNA take the 58 samples and create a sort of composite Caucasus "profile" to which each customer's DNA is compared?

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    I'm not sure but my guess is that they associate certain snps in the DNA with certain groups. Then they do a composite with the various reference samples.

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    Quote Originally Posted by Apex n Harmony View Post
    Does anyone know how exactly a customer's DNA is compared to the reference panel? I've read the ethnicity white paper, but I still don't fully understand the details.

    For example, the Caucasus region includes 58 samples (although we don't how many samples were taken from each country in the defined region, or whether at least one sample was taken from each country). Is each customer's DNA compared to each of the 58 individual samples from the Caucasus, or does AncestryDNA take the 58 samples and create a sort of composite Caucasus "profile" to which each customer's DNA is compared?
    It is based on allele frequencies as described under section 4.
    "The next step is to estimate a customer’s ethnicity based on the DNA of the reference set of samples, as well as the DNA of the customer. We assume that an individual’s DNA is a mixture of DNA from a set of “source” reference populations. In the example below, a sample gets each allele at each SNP from one of four “source” reference populations.
    Figure 4.1: Example Customer Genotype. The table indicates the genotypes of the sample. The colors of the SNPs correspond to their locations of origin, indicated in the legend beside the table.
    In order to make estimates of genetic ethnicity, we simply use what we know about the frequency of the alleles of those SNPs in the reference populations.

    In this example, we are looking at the frequencies of the two alleles at the first SNP in each of the four reference populations. A’s are more common in Eastern Europeans and people from the Iberian Peninsula, A’s and G’s are equally likely in the Irish (from the Ireland region), and G’s are more likely in Central Asians. If a sample from an individual has two A’s, it seems that Eastern Europe and the Iberian Peninsula are the more likely places from which he or she may have gotten these two alleles. In our example, the individual has gotten 1 A from Eastern Europe, and 1 A from the Iberian Peninsula.
    AncestryDNA uses similar reasoning to make our actual estimates, but with a rigorous statistical model that incorporates SNP data from across the genome."

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  13. #19
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    It would be interesting to know which of those reference samples scored 100% representative of their region. For Iberian Peninsula I believe it's some Basque samples. I'm curious about the rest of the regions.

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    Quote Originally Posted by mwauthy View Post
    It would be interesting to know which of those reference samples scored 100% representative of their region. For Iberian Peninsula I believe it's some Basque samples. I'm curious about the rest of the regions.
    My father got pretty close: 96% Caucasus. Three of his grandparents were from the Gilan Province in Iran (we think), and the fourth was from Tehran (we think). I don't think I've seen a higher Caucasus score on AncestryDNA. I've seen an Armenian score 66% and an Azerbaijani score 69%, and I've seen Iranians score anywhere from 60% to 96%.

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