Date of Award
Summer 7-8-2025
Document Type
Thesis
Degree Name
Master of Science (MS)
Department/Program
Forensic Science
Language
English
First Advisor or Mentor
Mechthild Prinz
Second Reader
Richard Li
Third Advisor
Ashley Morgan
Abstract
This study compares the performance of two capillary electrophoresis instruments—the SeqStudio™ Genetic Analyzer and the 3500™ Genetic Analyzer—for forensic short tandem repeat (STR) analysis. Using the GlobalFiler STR kit and certified reference material (SRM 2391d), five key performance metrics were evaluated: sizing precision, signal reproducibility, detection sensitivity, mixture resolution, and overload tolerance. STR profiles were generated from single-source and mixture samples with DNA inputs ranging from 500 pg to 15.6 pg. Both instruments met the < 0.15 bp sizing precision requirement for forensic casework. Signal reproducibility tests showed that the SeqStudio often produced higher average RFU values, but with greater variability, while the 3500 demonstrated more stable signal performance across days and samples. Mixture detection was effective on both platforms up to 1:10 ratios. Dropout of minor alleles began to appear at 1:20 ratios, especially in green and yellow dye channels, on both instruments. Sensitivity studies confirmed full profile recovery down to 62.5 pg, with increasing allelic and locus dropout at lower inputs. Enhanced injection voltage (1.5 kV) did not improve low-template performance. In overload testing (1–5 ng input), the 3500 maintained a consistent signal output, while the SeqStudio exhibited signal suppression at 5 ng, likely due to internal normalization. The SeqStudio exhibited better spectral overlap compensation, with fewer occurrences of spectral bleed-through artifacts. These findings support the use of both platforms in forensic casework, while emphasizing the importance of platform-specific calibration and analytical threshold settings for optimal performance.
Recommended Citation
Leichyk, Yana, "STR Analysis Performance Comparison for two Capillary Electrophoresis Instruments: the SeqStudio and the 3500 Genetic Analyzers" (2025). CUNY Academic Works.
https://academicworks.cuny.edu/jj_etds/356
