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Mixtures with relatives and linked markers

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Abstract

Mixture DNA profiles commonly appear in forensic genetics, and a large number of statistical methods and software are available for such cases. However, most of the literature concerns mixtures where the contributors are assumed unrelated and the genetic markers are unlinked. In this paper, we consider mixtures of linked markers and related contributors. If no relationships are involved, linkage can be ignored. While unlinked markers can be treated independently, linkage introduces dependencies. The use of linked markers presents statistical and computational challenges, but may also lead to a considerable increase in power since the number of markers available is much larger if we do not require the markers to be unlinked. In addition, some cases that cannot be solved with an unlimited number of unlinked autosomal markers can be solved with linked markers. We focus on two special cases of linked markers: pairs of linked autosomal markers and X-chromosomal markers. A framework is presented for calculation of likelihood ratios for mixtures with general relationships and with linkage between any number of markers. Finally, we explore the effect of linkage disequilibrium, also called allelic association, on the likelihood ratio.

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Authors and Affiliations

  1. Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Aas, Norway

    Guro Dørum, Daniel Kling & Thore Egeland

  2. Department of Family Genetics, Norwegian Institute of Public Health, Oslo, Norway

    Daniel Kling

  3. Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden

    Andreas Tillmar

  4. Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden

    Andreas Tillmar

  5. Department of Medical Genetics, University of Oslo and Oslo University Hospital, Oslo, Norway

    Magnus Dehli Vigeland

Authors
  1. Guro Dørum
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  2. Daniel Kling
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  3. Andreas Tillmar
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  4. Magnus Dehli Vigeland
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  5. Thore Egeland
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Correspondence to Guro Dørum.

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Dørum, G., Kling, D., Tillmar, A. et al. Mixtures with relatives and linked markers. Int J Legal Med 130, 621–634 (2016). https://doi.org/10.1007/s00414-015-1288-x

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  • DOI: https://doi.org/10.1007/s00414-015-1288-x

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