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Chromosomal Duplications Along the Y-Chromosome and Their Potential Impact on Y-STR Interpretation



John M. Butler, Amy E. Decker, Margaret C. Kline, Peter M. Vallone


Y-chromosome short tandem repeat (Y-STR) markers are being touted as potential tools for distinguishing low levels of male DNA in the presence of excess female DNA as is present in many sexual assault samples. Usually single copy Y-STR loci produce a single amplicon in single source samples, and thus the observation of multiple peaks at such a locus could suggest to an analyst that a mixture of more than one male contributor is present in the tested sample. However, many regions of the Y-chromosome are duplicated or even triplicated in some individuals and this fact can thus complicate potential mixture interpretation. Reasons for the presence of duplications at multiple loci within a single sample are explored in the context of Y-STR marker location along the chromosome. True male-male mixtures commonly exhibit more than one locus-specific PCR product across multiple Y-STR loci that are not adjacent to one another on the Y-chromosome. In addition, duplicated loci typically possess alleles that differ by only a single repeat unit and possess similar peak heights.
Journal of Forensic Sciences
No. 4


DNA interpretation, DNA mixtures, DNA typing, forensic science, short tandem repeat, Y-chromosome


Butler, J. , Decker, A. , Kline, M. and Vallone, P. (2005), Chromosomal Duplications Along the Y-Chromosome and Their Potential Impact on Y-STR Interpretation, Journal of Forensic Sciences (Accessed April 24, 2024)
Created July 1, 2005, Updated February 17, 2017