An important forensic application for Y-chromosome short tandem repeats (Y-STRs) is the identification of male DNA. Since the Y-chromosome is non-recombining and most Y-STRs have slippage mutation rates on the order of 1x10-3 or lower, Y-STR commercial multiplex systems do not yet allow personal individualization. This is problematic in criminal investigations where the persons of interest include males of the same paternal line. In order to obtain discrimination among paternal male relatives, it would be necessary to use a larger number of Y-STRs or a selection of Y-loci with higher slippage mutations with the hope of encountering a germline meiotic mutation. In this study, Y-STR loci from three multiplexes were examined: an ultra-high discrimination multiplex of 14 non-core loci; Promega's PowerPlex® Y23; and a rapidly mutating 13-locus panel (mutation rates above 1x10-2). Taking the three multiplexes together provides a unique 40-locus Y-STR panel (the "Masker Set"), a powerful tool to separate closely related males. The loci were examined for discriminative slippage mutations in pairs of paternally related South Brazilian males: 99 grandfather-grandson, 103 uncle-nephew, and 140 brothers. The goal of this study was to analyze the "Masker Set" loci by: describing the characteristics and frequency of germ-line mutations; noting differences in mutation rates between and within loci; determining repeat gain and loss rates; and identifying the most informative loci to differentiate male relatives. Using the "Masker Set", pairs of male relatives were distinguished by at least one mutation 53% of the time for grandfather-grandson, 62% for uncle-nephew, and 54% for brothers. The most discriminating Y-STR loci were: DYF387S1, DYF404S1, DYS526B, DYS389II, DYS449, DYS547, DYF399S1, DYS458, DYS576, DYF403S1A, DYS508, DYS612, DYS403S1B, DYS518, and DYS627.
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Master of Science (M.S.)
College of Sciences
Forensic Science; Forensic Biochemistry
Length of Campus-only Access
Masters Thesis (Campus-only Access)
Masker, Nicole, "The Estimation of Germ Line De Novo Mutation Rates of Extended Sets of Y-STR Haplotypes to Aid in the Differentiation of Male Biological Relatives in Criminal Investigations" (2016). Electronic Theses and Dissertations. 5621.