Usefulness of the X-chromosome on forensic science

In kinship analyses, as well as in other forensic studies, autosomal markers are, generally, the tool of choice. However, there are some more complex situations where the study of these markers is not sufficiently informative and the analysis of the available set of markers proves to be inconclusive. Due to its characteristic transmission properties, the X-chromosome markers have emerged as an asset in certain genealogical situations, not only complementing and completing autosomal marker information but also by solving alone certain kinship studies irresolvable with autosomal markers. Examples of this application can occur in complex genealogical analyses, or when the alleged father is not available (in such cases the statistical evidence given by autosomal markers is, in most cases, ambiguous), or when the kinship alternatives are genetically indistinguishable using autosomal markers (e.g., as in the cases of half-siblings, avuncular, or grandparent-grandchild kinships).