All ETDs from UAB

Advisory Committee Chair

Jason G Linville

Advisory Committee Members

Elizabeth A Gardner

Asim K Bej

Document Type

Thesis

Date of Award

2016

Degree Name by School

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

Abstract

As instruments for detecting DNA have become more sensitive and reagents for amplifying DNA become more effective, forensic DNA analysts have obtained short tandem repeat (STR) profiles from evidence containing a small amount of DNA. Sources, such as dandruff, sweat, and saliva, which were once thought to be inadequate for STR profiling, can now be analyzed to effectively establish a profile. These low quantities of DNA can be recovered from liquid samples, such as saliva, or extracted and concentrated from large volumes of buffer, then amplified to give a DNA profile. This study focused on recovering saliva from drinking containers. When drinking from a container, a person leaves epithelial cells on the top of the container. A person also transfers epithelial cells to the inside, bottom of the container. Currently, the method for testing drinking containers, such as a bottled water, is to swab the top of the bottle and analyze the swabs for DNA. The tops of bottles are exposed, leading to the possibility that a person may contaminate or destroy any epithelial cells that remain on the top of a bottle. The bottom of a bottle has more protection from the outside environment, and there could be more DNA recovered from the bottom of the bottle than the top. For this study, water bottles collected after consumption by volunteers were swabbed at the top to collect saliva, and saliva in the remaining water was collected from inside the bottom. The goal was to compare the established method of swabbing drinking containers to a new method that was formed in this study and determine which method is better to use in a forensic crime lab. Different methods for collecting DNA from the liquid remaining in drinking containers were also evaluated. The results of this study indicate that evaporation is a more effective method of concentrating DNA than pelleting cells. Both evaporation methods yielded higher amounts of amplified alleles than pelleting cells. Of the two evaporation methods evaluated, the nitrogen evaporator with a water bath was a better method than the oven. The nitrogen evaporator dried samples faster than the oven. The findings of this study also show that collecting DNA with lysis buffer is more effective than swabbing. Collection with lysis buffer is better when processing plastic bottles and eliminates a step in extraction. When evaluating the four combinations of concentrating and collecting DNA, the nitrogen evaporator with lysis buffer is the best method as the samples dry faster and an extraction step is eliminated. When evaluating the samples collected from volunteers, the results show that as the remaining water in the bottles decreased, the DNA left in the liquid also decreased. The samples with the 40 mL of liquid remaining contain the highest average amount of DNA and result in the largest amount of alleles amplified. For comparison to the established method of swabbing the tops of plastic bottles, the findings show that both methods contain similar amounts of DNA. The established method results in the highest amount of alleles amplified. These results show that the current method of processing bottles is better, but targeting the backwash in bottles is viable option for forensic biologists to consider.

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