Utilization of X-chromosomal markers in forensic genetics

Apart from some exceptions typing of autosomal short tandem repeats is normally sufficient for kinship testing in the standard trio situation consisting of the mother, child and putative father. Nevertheless, there are some constellations, such as deficiency and incest cases, which require X-chromosomal typing. However, application is only possible in X-chromosomal inheritance lineages. X-chromosomal haplotyping is suitable for proving distant kinship, such as aunt/niece or first cousins. As male individuals only have one X chromosome the haplotype can be directly recognized by typing the markers and both haplotypes of female individuals often can be deduced from pedigree analysis. X-chromosomal testing can be effective in incest cases or to solve cases in which two alleged fathers are related. In forensic stain analysis X-chromosomal analyses should be utilized when a female component has to be identified in a mixture contaminated with male components. A series of ethical aspects have to be considered when X-chromosomal markers are investigated.