Date of Award
Summer 8-2025
Document Type
Thesis
Degree Name
Master of Science (MS)
Department/Program
Forensic Science
Language
English
First Advisor or Mentor
Lissette Delgado-Cruzata
Second Reader
Marta Concheiro-Guisan
Third Advisor
Sai Casado Zapico
Abstract
Monozygotic (MZ) twins possess identical DNA sequences, posing a problem for forensic scientists, as they are incapable of distinguishing MZ twins from each other using traditional DNA identification methods. However, the epigenomes of MZ twins will differ and might be used for their forensic discrimination. Here, we explored the variability of an assay previously developed by our laboratory that showed high discrimination potential for MZ twins using buccal swab DNA, cg18562578 MethylQuant. We measured precision at each step: bisulfite conversion, nested PCR, and qPCR, reproducibility, and repeatability. DNA methylation ratios were compared between two analysts carrying each step using the same samples. We found no difference between analysts for bisulfite conversion (0.4±0.2 vs 0.03±0.003, p=0.13), qPCR (0.1±0.04 vs 0.2±0.07, p=0.12), inter-laboratory reproducibility (5.6±5.2 vs 1.6±1.2, p=0.4), and inter- (0.04±0.02 vs 2.2±1.1, p=0.18) and intra-repeatability (0.6±0.02 vs 0.5±0.04, p=0.59). However, samples from two analysts performing the nested PCR step had different DNA methylation ratio levels (0.3±0.1 vs. 0.002±0.005, p=0.03). The coefficients of variation (CV) for the qPCR steps were 70.4-74.4%, but CV for intra-plate repeatability was 9.6% suggesting that for discrimination under this assay MZ twins samples must be processed together for minimal variation. In future studies, we will explore the variability of the nested PCR step of this assay.
Recommended Citation
Arnold, Sydney E., "Exploring variability of the cg18562578 MethylQuant assay for the forensic discrimination of monozygotic twins" (2025). CUNY Academic Works.
https://academicworks.cuny.edu/jj_etds/358
Included in
Forensic Science and Technology Commons, Genetics Commons, Molecular Biology Commons, Molecular Genetics Commons
