title: X-chromosome markers in kinship testing: a generalisation of the IBD approach identifying situations where their contribution is crucial.
abstract: The standard practice of forensic kinship evaluation uses unlinked autosomal markers. However, X-chromosome markers have recently gained recognition as a powerful tool to complement the information provided by autosomes, particularly in complex cases. In this paper, the X-chromosome mode of transmission is addressed in the theoretical identity-by-descent framework. Formulas for the joint genotypic probabilities considering various pedigrees relating two inbred and/or non-inbred individuals are derived. Finally, the importance of X-chromosome markers is highlighted by the fact that, in addition to complementing the autosomal information, X-chromosome transmission allows differential weighting of certain hypotheses regarding pedigrees belonging to the same autosomal class, i.e., pedigrees that are indistinguishable by the use of unlinked autosomal markers. Illustrative examples of common kinship testing are shown.
authors.affiliation: IPATIMUP, Instituto de Patologia e Imunologia Molecular da Universidade do Porto, Porto, Portugal. npinto@ipatimup.pt
authors.forename: Nádia
authors.initials: N
authors.lastname: Pinto
authors.forename: Leonor
authors.initials: L
authors.lastname: Gusmão
authors.forename: António
authors.initials: A
authors.lastname: Amorim
mesh_terms: D000483:Alleles; D041321:Chromosomes, Human, X; D005190:Family; D005260:Female; D053803:Forensic Genetics / Q000379:methods*; D005787:Gene Frequency; D008040:Genetic Linkage; D056426:Genetic Loci; D005819:Genetic Markers; D005838:Genotype; D006801:Humans; D008297:Male; D008957:Models, Genetic; D010375:Pedigree
chemical_list: D005819:Genetic Markers