Life Sciences Commons^™

Extraction Of Challenging Forensic Samples Using The Microgem Dna Extraction Kit, Falyn R. Vega

Student Theses

In forensic science, DNA extraction can be a tedious and resource-intensive process. Extraction with Proteinase K is an industry standard but has its drawbacks, such as requiring multiple ionic detergents and washing steps. MicroGEM has developed a new enzyme called forensicGEM that is temperature-dependent and compatible with mesophilic enzymes, offering complete DNA extraction in about 20 minutes in a single tube, limiting contamination, loss of sample, and working time. ForensicGEM can extract DNA from highly degraded samples, potentially leading to more complete STR profiles. Highly degraded tissue and bone samples were collected and extracted with the forensicGEM …

Signature Peptide Identification For Body Fluids In Sexual Assault Cases By Liquid Chromatography Tandem Mass Spectrometry (Lc-Ms/Ms), Kelci Somers

Student Theses

Body fluids contain proteins that perform functions specific to different types of body fluids. Therefore, the detection of signature peptides for these proteins can potentially identify a body fluid in a forensic investigation. This project aimed to validate a method to detect signature peptides in body fluids commonly found in sexual assault cases by LC-MS/MS. Signature peptides for semen and saliva fluids were combined with two signature peptides for vaginal fluids. Samples created using two donors each for saliva, semen, and vaginal fluids were extracted using a trypsin digest, with separation of the protein and DNA fractions. The LC-MS/MS was …

Reproducibility Of Individual Dna Deposits Detected Through Cellular Fluorescence, Natalee Small-Davidson

Student Theses

Contact traces are an important part of DNA casework, but the probative value of any identified associations depends on the possibility of passive transfer. There is known individual variation in DNA left behind during contact, this DNA shedding propensity has an effect on whose DNA is detected. This study evaluated this variability using a cell staining approach. Volunteers were asked to deposit a fingerprint on a clean glass slide, then wash their hands and deposit a second fingerprint after a 30-minute wait without touching anything. Three sets of samples were collected over three consecutive weeks. Fingerprints were stained with a …

Determination Of Human Shedding Propensity Based On Str Results, Genevieve Trapani

Student Theses

Trace DNA evidence may be discovered at a crime scene after having been deposited by a person of interest via active or passive transfer. Based on previous studies, passive transfer of one’s DNA is influenced by their shedding propensity, or probability of depositing a detectable amount of DNA through touch. Determining the shedding propensity of a person of interest can aid in trace DNA interpretation in forensic casework. This study explored STR profile quality and the presence of a DNA mixture for different skin surface locations, including fingertips before and after handwashing. As expected, unwashed fingers showed a higher prevalence …

Performance Of A Dna And Protein Co-Extraction With Trypsin In Comparison To Two Proteinase K Based Dna Extraction Methods, Dinura A. Gunatilake

Student Theses

Effective DNA extraction methods are important for forensic applications. The main goal of this experiment was to determine if a newly developed trypsin based protein/DNA co-extraction method applied to contact traces would yield comparable results to a commercial Proteinase K method (QIAamp DNA Investigator Kit) and a Chelex extraction method with Tween 20 used in forensic laboratories. This was tested on 20 sets of sebaceous fingerprints on glass slides.

The results of this study demonstrate the trypsin co-extraction method yielded the highest amount of DNA. In the first comparison, the mean total DNA yields for the trypsin-co extraction method and …

Discrimination Of Monozygotic Twins Using Dna Methylation Levels Of One Cpg Site At Chromosome 3, Dino O. Robinson

Student Theses

Conventional STR typing, commonly used in forensics for human identification, poses a problem in criminal cases and paternity disputes involving monozygotic (MZ) twins because they share identical DNA sequences. To date, no routine method is available in forensics to differentiate between individuals of MZ pairs. Recently, epigenetic methods measuring differential DNA methylation patterns have been applied to MZ twin differentiation. In this study, we investigated the potential to identify MZ twins using a previously identified DNA methylation site in chromosome 3, cg18562578, in a sample of 129 MZ and 37 dizygotic (DZ) twin pairs. We used bisulfite converted saliva DNA …

Range Of Detection For Proteins And Dna From Fingerprints On Fired And Unfired Cartridge Casings, Stacey-Ann R. Sterling

Student Theses

Cartridges and spent cartridge casings can be probative pieces of evidence. Unfortunately due to a combination of factors such as exposure to high temperatures and initially low amounts of biological material on the surface, DNA testing so far has been mostly unsuccessful for these items. Typing other marker systems, such as protein polymorphisms, on the same biological evidence would add power of discrimination. To explore this option we developed a DNA-protein trypsin-based co-extraction method that was optimized for unfired and fired cartridges. Various sample wet and dry collection methods and multiple metal casings, such as aluminum, nickel, steel, and brass …