Using X-chromosomal markers in relationship testing: How to calculate likelihood ratios taking linkage and linkage disequilibrium into account
2011 (English)In: Forensic Science International: Genetics, ISSN 1872-4973, Vol. 5, no 5, 506-511 p.Article in journal (Refereed) Published
X-chromosomal markers in forensic genetics have become more widely used during the 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 efficient model for calculating likelihood ratio (LR) 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 LR 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 presented model is an efficient way of doing so.
Place, publisher, year, edition, pages
Elsevier , 2011. Vol. 5, no 5, 506-511 p.
X-chromosome, Linkage, Linkage disequilibrium, Simulation, Haplotype frequency
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-54741DOI: 10.1016/j.fsigen.2010.11.004ISI: 000294297700023OAI: oai:DiVA.org:liu-54741DiVA: diva2:309701