All ETDs from UAB

Advisory Committee Chair

Jason G Linville

Advisory Committee Members

Elizabeth A Gardner

Harvey Hou

Document Type

Thesis

Date of Award

2020

Degree Name by School

Master of Science in Forensic Science (MSFS) College of Arts and Sciences

Abstract

This study focuses on two areas of interest when performing differential extractions for sexual assault kit analysis. By choosing different collection substrates, a traditional cotton swab, a nylon flocked swab, and a teased cotton swab, cellular elution capabilities were compared using two different semen dilutions. Nylon flocked swabs showed the most promise in obtaining a better male DNA yield compared to other swab types of similar dilution sets. Differential extraction methods introducing enzymatic digestion steps were modified and paired with the Qiagen DNA Investigator kit protocol to investigate their effects on cellular elution, cell separation, and time. These modified methods were compared to a standard differential extraction. DNase I is a highly selective nuclease that degrades excess free female DNA in the male sperm cell fraction before lysis. Cellulases from microorganisms have been reported to breakdown cellulose in cotton swabs and have therefore become a focus on cellular elution of sperm cells from cotton swabs. The alkaline lysis with DNase I was quicker than the other extraction methods but yielded very little DNA in the extractions and, therefore, the effect of DNase I on the reduction of female DNA carryover was not evaluated. Cellulase extraction techniques were applied to cotton swabs and teased cotton to determine if teasing the swab tips could enhance cellular elution after a differential extraction detergent buffer was applied. However, all modified methods did not release more male DNA from collection swabs when compared to the standard differential extraction.

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