Date of Award

Spring 5-2020

Document Type


Degree Name

Master of Science (MS)


Forensic Science



First Advisor

Lissette Delgado-Cruzata

Second Reader

Martin Rivas

Third Advisor

Mechthild Prinz


Conventional STR typing, commonly used in forensics for human identification, poses a problem in criminal cases and paternity disputes involving monozygotic (MZ) twins because they share identical DNA sequences. To date, no routine method is available in forensics to differentiate between individuals of MZ pairs. Recently, epigenetic methods measuring differential DNA methylation patterns have been applied to MZ twin differentiation. In this study, we investigated the potential to identify MZ twins using a previously identified DNA methylation site in chromosome 3, cg18562578, in a sample of 129 MZ and 37 dizygotic (DZ) twin pairs. We used bisulfite converted saliva DNA and a 2-step methylation-specific qPCR method to determine DNA methylation at this site. We investigated differences between MZ and DZ twins as well as within MZ twin pair differences. We found that MZ and DZ twin pair differences were not statistically significant (0.39±0.29 vs 0.46±0.41, p-value=0.38) suggesting that DNA methylation at this site in the genome is not directly related to genetics. In addition, DNA methylation differences between MZ twins in a pair were found to be statistically significant (0.39±0.30 vs 0.78±0.29, p-value=0.00001). However, for 22% of the MZ pairs with DNA methylation differences below 0.1, there is no statistically significant difference to allow for discrimination. While more research needs to be conducted, this study highlights the potential of DNA methylation markers in the discrimination of MZ twins using saliva DNA

Available for download on Sunday, November 01, 2020