Correspondence
In Reply
The correspondent questions the development of reference data for DNA-based biogeographic ancestry analysis. Unfortunately, we were not able in our article (1) to explain this topic in detail owing to reasons of space constraints.
Different genome-wide studies of various human population samples worldwide, and their specific statistical data analyses, have shown that based on such data, individuals form groups that can be distinguished from one another on the basis of the individual’s genomic data similarities or lack thereof (for example [2]).
The biogeographic ancestry or the appearance phenotypes of the studied individuals did not play any part in these genomic groupings. Retrospective inspection of the geographical origin of the studied individuals demonstrated that these genomic similarity groups corresponded to the continental regions of biogeographic ancestry of the studied individuals. This can be explained by the fact—among others—that families often live in one continental region over many generations, and tend to mix with people within their own continental region, rather than with people from distant continental regions.
Such population genetic studies form the foundation of genomic control analyses, which are undertaken when developing reference data sets for the biogeographic ancestry analysis. These are based on hundreds of thousands of genome-wide distributed DNA markers (single nucleotide polymorphisms, SNPs) and specific statistical analysis methods, which allow continental assignment and the finding of possible genetic-geographical admixture. In the result of these genomic control analyses, only data from those samples are finally used as reference data for biogeographic ancestry analysis that show the expected genomic similarity with other samples from the same continental region of origin. Samples that in such genomic control analyses showed none or only a very limited genomic similarity with other samples from the same continental region of origin—for example, because of genetic ancestors from different continental regions—are not included in the reference data set for the biogeographic ancestry analysis.
DOI: 10.3238/arztebl.2020.0269b
On behalf of the authors
Prof. Dr. rer. nat. Manfred Kayser
Department of Genetic Identification
Erasmus MC University Medical Center Rotterdam
Rotterdam, Niederlande
Conflict of interest statement
Prof. Kayser is a co-inventor of patent no. EP2195448A1 (“Method to predict iris color”) but receives no license fees or royalties from this. He has appeared as an invited speaker at scientific meetings, with reimbursement of meeting participation fees and of travel and accommodation expenses by Thermo Fisher Scientific, Promega, and the Wenner-Gren Foundation. He is commissioned to provide medicolegal expert reports on DNA trace analysis for the investigative authorities in multiple countries.
Prof. Kayser served until April 2018 as member of the Scientific Advisory Board of Identitas Inc., without receiving honoraria or other payments for this activity.
| 1. | Schneider PM, Prainack B, Kayser M: The use of forensic DNA phenotyping in predicting appearance and biogeographic ancestry. Dtsch Arztebl Int 2019; 116: 873–80 VOLLTEXT |
| 2. | Li JZ, Absher DM, Tang H, et al.: Worldwide human relationships inferred from genome-wide patterns of variation. Science 2008; 319: 1100–4 CrossRef MEDLINE |
