Date of Submission

5-13-2020

Document Type

Thesis

Advisor

Angie Ambers, Ph.D

Keywords

DNA Damage, Household/Commercial Bleach, Full Genetic Profile, Forensic Laboratories, DNA Evidence

MeSH

DNA Damage, Sodium Hypochlorite, Genetic Profile

LCSH

DNA damage, Sodium hypochlorite, Crime laboratories, Crime scenes

Abstract

Household/commercial bleach (6% NaOCl, sodium hypochlorite) degrades DNA through oxidative damage, production of chlorinated base products, and cleavage of DNA strands (breaking it into smaller and smaller fragments). The presence of these lesions significantly impacts the ability to generate a full genetic profile from an evidentiary sample. In fact, knowledge of the damaging effect of bleach on DNA is the basis for its use in forensic laboratories to clean workbenches and prevent cross-contamination of samples between cases. Additionally, bleach is used intentionally by criminals to clean up crime scenes and destroy DNA evidence. A previous study demonstrated that bleach has a decreased effect on native DNA that is still encompassed within a body fluid (compared to naked DNA that has already been extracted) (Ambers et al. 2014). This research project expanded on the previous study, with an increased sample size and expanded data set. Numerous variables were tested, including dried blood, wet (uncoagulated) blood, native DNA, naked DNA, dried semen, wet (liquid) semen, and varying concentrations of bleach. DNA in whole human blood or semen (native conformation) and extracted (naked) DNA were immersed in two different concentrations of bleach for a 1-hour exposure period. Solid-phase DNA extraction and human-DNA-specific quantification revealed that sufficient quantities of DNA were recovered for STR typing, for both native and naked DNA templates and after exposure to both bleach concentrations (with higher DNA recovery from native samples vs. naked templates).

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