Using X-chromosomal markers in relationship testing: Calculation of likelihood ratios taking both linkage and linkage disequilibrium into account

X-chromosomal markers in forensic genetics have become more widely used during recent years, particularly for relationship testing. Linkage and linkage disequilibrium (LD) must typically be accounted for when using close X-chromosomal markers. Thus, when producing the weight-of-evidence, given by a DNA-analysis with markers that are linked, the normally used product rule is invalid. Here we present an implementation of an efficient model for calculating likelihood ratios (LRs) with markers on the X-chromosome which are linked and in LD. Furthermore, the model was applied on several cases based on data from the eight X-chromosomal loci included in the Mentype® Argus X-8 (Biotype). Using a simulation approach we showed that the use of X-chromosome data can offer valuable information for choosing between the alternatives in each of the cases we studied, and that the LR can be high in several cases. We demonstrated that when linkage and LD were disregarded, as opposed to taken into account, the difference in calculated LRs could be considerable. When these differences were large, the estimated haplotype frequencies often had a strong impact and we present a method to estimate haplotype frequencies. Our conclusion is that linkage and LD should be accounted for when using the tested set of markers, and the used model is an efficient way of doing so.

Egeland, TUniversitetet i Oslo,University of Oslo,Høgskolen i Oslo og Akershus (HiOA),Oslo and Akerhus University of Applied Sciences (author)
Lindblom, BLinköpings universitet,Linköping University (author)
Holmlund, GLinköpings universitet,Linköping University (author)
Mostad, Petter,1964Gothenburg University,Göteborgs universitet,Institutionen för matematiska vetenskaper, matematisk statistik,Department of Mathematical Sciences, Mathematical Statistics,Chalmers tekniska högskola,Chalmers University of Technology,University of Gothenburg(Swepub:cth)mostad (author)
Linköpings universitetUniversitetet i Oslo (creator_code:org_t)

In:Forensic Science International: Genetics: Elsevier BV5:5, s. 506-5111872-49731878-0326

By the author/editor: A.O., Tillmar; Egeland, T; Lindblom, B; Holmlund, G; Mostad, Petter, ...

About the subject

NATURAL SCIENCES: NATURAL SCIENCES; and Mathematics; and Probability Theo ...

NATURAL SCIENCES: NATURAL SCIENCES; and Biological Scien ...; and Bioinformatics a ...

By the university: University of Gothenburg; Chalmers University of Technology

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