Validation and casework application of a Y chromosome specific STR multiplex

Area of Science:

• Forensic Science
• Genetics
• Molecular Biology

Background:

• Short tandem repeat (STR) analysis is crucial in forensic DNA profiling.
• Y-chromosome specific STRs offer unique advantages for specific forensic scenarios.
• Validation of new multiplex systems is essential for reliable application.

Purpose of the Study:

• To validate a Y-chromosome specific STR multiplex system according to TWGDAM guidelines.
• To assess the performance of the Y STR multiplex in terms of stability, robustness, and sensitivity.
• To evaluate the utility of Y STR typing for analyzing DNA mixtures and challenging samples.

Main Methods:

• Performed validation experiments following TWGDAM guidelines.
• Utilized Perkin-Elmer 373 and 377 automated sequencers with two-color labeling.
• Conducted mixture studies with male and female DNA admixtures.
• Compared Y STR typing results with autosomal STR typing on nonprobative semen samples.

Main Results:

• The Y STR multiplex system exhibited excellent stability, robustness, and sensitivity.
• Mixture studies showed a cutoff rate comparable to autosomal STRs, with no interference from female DNA.
• Y STR typing demonstrated a higher success rate than autosomal typing for detecting semen donor alleles.
• Case examples highlighted the system's effectiveness in confirming exclusions and clarifying complex mixtures.

Conclusions:

• The validated Y STR multiplex system is a reliable tool for forensic DNA analysis.
• Y STR typing is particularly useful for resolving complex mixtures and identifying multiple male contributors.
• This Y STR multiplex system represents a valuable enhancement to the forensic DNA testing toolkit.