ISSN: 0022-1198
CODEN: JFSCA
Published Online: 25 May 2005
Page Count: 7

Chromosomal Duplications Along the Y-Chromosome and Their Potential Impact on Y-STR Interpretation
Decker, AE
National Institute of Standards and Technology, MD

Butler, JM
National Institute of Standards and Technology, MD

Kline, MC
National Institute of Standards and Technology, MD

Vallone, PM
National Institute of Standards and Technology, MD

(Received 13 November 2004; accepted 5 February 2005)

Abstract

Y-chromosome short tandem repeat (Y-STR) markers are being used 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.

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

Paper ID: JFS2004481
DOI: 10.1520/JFS2004481
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