Analysis of linkage and linkage disequilibrium for eight X-STR markers
Journal article, 2008

X-chromosomal short tandem repeats (X-STR) have proven to be informative and useful in complex relationship testing. Themain feature of X-STR markers, compared to autosomal forensicmarkers, is that all loci are located on the same chromosome. Thus, linkage and linkage disequilibrium may occur. The aim of this work was to study population genetic parameters of eight X-STR markers, located in four linkage groups. We present haplotype frequencies, based on 718 Swedish males, for the four linkage groups included in the Argus X-8 kit. Forensic efficiency parameters have been calculated as well as the allelic association between the tested markers for detection of linkage disequilibrium. To study the occurrences of recombination between the loci, both Swedish and Somali families were typed. A mathematical model for the estimation of recombination frequencies is presented and applied on the family samples. Our study showed that the tested markers all have highly informative forensic values and that there is a significant degree of linkage disequilibrium between the STR markers within the four linkage groups. Furthermore, based on the tested families, we also demonstrated that two of the linkage groups are partially linked. A consequence of these findings is that both linkage and linkage disequilibrium should be accounted for when producing likelihood ratios in relationship testing with XSTR markers.

X-chromosomal STR Linkage Linkage disequilibrium Recombination Likelihood ratios Sweden

Author

Andreas O Tillmar

Linköping University

Petter Mostad

University of Gothenburg

Chalmers, Mathematical Sciences, Mathematical Statistics

Thore Egeland

Oslo Metropolitan University

Oslo University Hospital

Bertil Lindblom

Linköping University

Gunilla Holmlund

Linköping University

Kerstin Montelius

Linköping University

Forensic Science International: Genetics

1872-4973 (ISSN)

1 37-41

Subject Categories

Probability Theory and Statistics

Forensic Science

DOI

10.1016/j.fsigen.2008.09.006

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1/5/2021 1