This article discusses the effects of electron beam irradiation on DNA typing.
United States mail confirmed to contain a pathogenic agent may undergo irradiation with electron beams, X-rays, or gamma rays. It has not yet been determined whether DNA can be isolated and typed from forensic evidence that has been sterilized by means of electron beam irradiation. This study sought to obtain DNA profiles from licked envelopes exposed to electron beam irradiation dosages consistent with those necessary to inactivate anthrax spores. Inactivation of the spores due to electron beam irradiation is a result of chemical bond breakage and DNA damage. It was assumed that human DNA trapped in the glue matrix of the envelopes would also sustain damage as a result of irradiation. Half of the 16 envelopes used in this study served as nonirradiated controls while the other half underwent irradiation at dosages sufficient to kill anthrax spores. Total cellular DNA was extracted from all envelopes; nuclear short tandem repeat loci, as well as the hypervariable region I from mitochondrial DNA, were amplified by means of the polymerase chain reaction. Short tandem repeat profiles and mitochondrial DNA sequence haplotypes were acquired on an ABI Prism 310 Genetic Analyzer platform. The results show that DNA profiles can be generated from evidence that has undergone measures to inactivate potential biological agents. While electron beam irradiation of licked envelopes at dosages of 29.3 kGy and 51.6 kGy potentially affected both the quality and quantity of human cellular DNA, the ability to obtain full nuclear STR profiles and mitochondrial HVI sequence haplotypes remained largely unaffected. Nuclear and/or mitochondrial DNA analysis should be considered as a means to identify individuals responsible for distributing biological agents even in the event the evidence in question has undergone irradiation prior to sample processing. 2 tables, 6 figures, 29 references
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