While forensic short tandem repeat (STR) sequencing assays include largely overlapping sets of markers, assay designs vary in polymerase chain reaction (PCR) priming sites, resulting in variable sequence ranges between assays. The 2024 Recommendations of the DNA Commission of the International Society for Forensic Genetics (ISFG) on STR Sequence Nomenclature [1] include a recommendation for a minimum sequence reporting range for each STR locus, with the goal of reducing ambiguity in the human- or software-determined “end” of the repeat. These standardized minimum ranges are intended to facilitate data transfer across laboratories and automated sequence searching; however, no single commercially available STR sequencing assay can currently meet the “ISFG minimum range” for all loci. A combination of two commercial assays can achieve the recommended minimum range for 27 autosomal STR loci, thus, population samples that have been sequenced with both assays can be used to produce sequence-based STR allele frequencies compliant with the ISFG minimum range. The NIST population samples have previously been sequenced and published for these 27 autosomal STR markers with one assay [2] and were recently sequenced with the additional assay required to achieve the ISFG minimum range. The STR sequence data from a set of 1043 population samples (four populations) successfully sequenced with both assays have been merged to produce an allele frequency dataset in the complete ISFG minimum range. This presentation describes the creation of this ISFG minimum range dataset, along with separate allele frequencies for each assay that represent the maximum reportable sequence range based on current information from the manufacturers. Additionally, the presentation will include updates to associated STR nomenclature resources aligned with the 2024 ISFG DNA Commission recommendations: the Forensic Sequence STRucture Guide (FSSG) [3], containing annotated human genome reference sequences for forensically relevant autosomal STR, Y-STR, and X-STR loci and the STR Sequencing Project (STRSeq, https://www.ncbi.nlm.nih. gov/bioproject/380127) [4], consisting of a curated catalog of over 2500 sequences from forensic STR loci.

Authors

• Katherine Gettings (National Institute of Standards and Technology, United States of America)
• Lisa Borsuk (National Institute of Standards and Technology, United States of America)
• Kevin Kiesler (National Institute of Standards and Technology, United States of America)
• Lauren Mullen (National Institute of Standards and Technology, United States of America)
• Peter Vallone (National Institute of Standards and Technology, United States of America)

References

[1]  Recommendations of the DNA Commission of the International Society for Forensic Genetics (ISFG) on Short Tandem Repeat sequence nomenclature. DOI: 10.1016/j.fsigen.2023.102946

[2]  Sequence-based U.S. population data for 27 autosomal STR loci. DOI: 10.1016/j.fsigen.2018.07.013

[3]  “The devil's in the detail“: Release of an expanded, enhanced and dynamically revised forensic STR Sequence Guide. DOI: 10.1016/j.fsigen.2018.02.017

[4]  STRSeq: A catalog of sequence diversity at human identification Short Tandem Repeat loci. DOI: 10.1016/j.fsigen.2017.08.017