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Characterization of X Chromosomal Short Tandem Repeat Markers for Forensic Use

NCJ Number
Date Published
November 2013
136 pages
Recognizing that the use of X chromosomal short tandem repeat (STR) markers in forensics has increased in the past decade due to its distinctive contributions, this project addresses two issues that have not yet been resolved in this effort: the need to know mutation rates in order to handle possible mismatches attributable to mutational events, as well as questions of independent assortment and linkage disequilibrium.
Any investigated circumstance in which at least one female is involved may benefit from the use of X chromosomal STR, which can be applied to cases of missing persons, criminal incest, immigration, deficiency paternity, or other questioned relationships. In-depth characterization of the marker system is the first step in maximizing the power of this additional tool in the forensic arsenal. Based on the study of 20,625 meioses in confirmed family trios or duos at the 15 X STR markers, 18 mutations were observed across 7 of the 15 markers and in all three U.S. population groups, resulting in an overall mutation rate of 8.73 x 10-4, which is similar to that reported for Y chromosomal and autonomic STRs, as well as other published studies of X STRs. Also, the potential use of gonosomal STR marks to aid in the interpretation of such mixtures was investigated, and a multiplex was developed and characterized for this purpose. This assay correctly identified the sex and minimum number of contributors in all cases of artificial and theoretical mixtures tested as part of the study. It correctly assigned the actual number and sex of contributors 62 percent of the time. 28 tables, 148 references, a listing of disseminated research products, and appended supplementary information

Date Published: November 1, 2013