A forensic multiplex of nine novel pentameric-repeat STRs

Area of Science:

• Forensic Genetics
• Molecular Biology
• Population Genetics

Background:

• Pentameric short tandem repeats (STRs) offer reduced stutter compared to tetrameric STRs, aiding complex DNA mixture interpretation.
• Current forensic multiplexes can be improved for better sensitivity and degraded DNA analysis.
• Novel Y-chromosome markers are valuable for sex determination and population studies.

Purpose of the Study:

• To develop and validate an 11-plex forensic assay utilizing nine novel pentameric STRs and two male-specific markers.
• To assess the forensic informativeness and performance of the new pentameric STRs in diverse populations.
• To evaluate the assay's sensitivity and efficacy with degraded DNA samples.

Main Methods:

• Design of an 11-plex assay including nine pentameric STRs and two male-specific markers (DYS391, Y-Indel rs2032678).
• Estimation of STR allele frequencies in African, European, and East Asian populations from the HGDP-CEPH panel, plus a Northwest Spanish sample.
• Assessment of forensic informativeness metrics, assay sensitivity, and performance on degraded DNA.

Main Results:

• The pentameric STR loci exhibited an average stutter ratio of 2.15%, substantially lower than the 7.32% observed in tetrameric STRs.
• Novel variation in Y-Indel rs2032678 was reported in its forensic application as a sex marker, with East Asian-specific data presented.
• The assay demonstrated good forensic sensitivity and the ability to genotype highly degraded DNA samples.

Conclusions:

• The developed 11-plex assay using pentameric STRs is a valuable tool for forensic identification and kinship analysis, particularly for improving mixed DNA profile interpretation.
• The inclusion of novel pentameric STRs and Y-chromosome markers enhances the assay's utility and forensic applicability.
• This assay represents a significant advancement in forensic DNA typing technology, offering improved accuracy and efficiency.