Forensic DNA Analysis, Sexual Assault Evidence, Cell Separation
Short Tandem Repeat (STR) analysis has become a valuable tool in identifying the source of biological stains, particularly from the investigation of sexual assault crimes. Difficulties in analysis arise primarily in the interpretation of mixed genotypes when cell separation of the sexual assailant's sperm from the victim's cells is incomplete. The forensic community continues to seek improvements in cell separation methods from mixtures for DNA typing. This report describes the use of laser microdissection (LMD) for the separation of pure populations of spermatozoa from two-donor cell mixtures. In this study, cell separation was demonstrated by microscopic identification of histologically stained spermatozoa and female buccal cell mixtures, and STR analysis of DNA obtained from the separated sperm cells. Clear profiles of the male donor were obtained with the absence of any additional alleles from the female donor. Five histological stains were evaluated for use with LMD and DNA analysis: hematoxylin/eosin, nuclear fast red/picroindigocarmine, methyl green, Wright's stain, and acridine orange. Hematoxylin/eosin out-performed all other stains however nuclear fast red/picroindigocarmine could be used satisfactorily with STR analysis. In addition, three DNA isolation methods were evaluated for LMD collected cells: QIAamp (Qiagen), microLYSIS (Microzone Ltd.) and Lyse-N-Go (Pierce Chemical Co.). MicroLYSIS performed poorly, yielding low levels of PCR product. Lyse-N-Go extraction was effective for the recovery of DNA from LMD collected sperm cells while QIAamp isolation performed best for the recovery of DNA from LMD collected epithelial cells. LMD is shown to be an effective, low-manipulation separation method that enables the recovery of sperm while excluding epithelial cell DNA.
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Master of Science (M.S.)
College of Arts and Sciences
Length of Campus-only Access
Masters Thesis (Open Access)
Sanders, Christine, "The Use And Development Of Laser Microdissection To Separate Spermatozoa From Epithelial Cells For Str Analysis" (2005). Electronic Theses and Dissertations, 2004-2019. 614.