Abstract
In modern forensic genetics, the analysis of DNA mixtures is a challenge because of the obstacles found in defining the number of contributors, especially when they exceed two. The goal of the present study was to find the most reliable method of detection for profiling the two-male and female-male mixtures obtained. Bloodstains, saliva, and body tissues from various crime scenes were obtained as samples. All samples for DNA profiling have been subjected to DNA extraction, amplification, separation, and detection. Results revealed that DNA profiling showed two-male and female-male mixtures. Results also showed the presence of a major and a minor male contributor in each genetic locus according to peak heights. Differential extraction provided a reliable method for separating female and male contributors from each other in the case of the female-male mixture. The profiling of the male donor in the female-male mixture was furtherly verified using the Y-STR profiling process. Eventually, we can infer that a good approach to identifying the two-male mixture is autosomal STR interpretation centered on major and minor differentiation. In addition, differential separation and Y-STR profiling proved to be the best processes for profiling mixed samples comprising female-male contributors as only the male profile was identified.
Highlights
Samples recovered for DNA analysis in a forensic crime scene often consist of mixtures of cells that may belong to the suspect, victim, and an infinite number of additional persons
Sobhy El-Sayed Hassab El-Nabi et al as the amount of DNA is abundant, the analysis of such evidence is relatively uncomplicated and as a result, the attribution of each individual in the collected sample can be determined and the allelic contributions to the DNA evidence of the known individual can be extracted from the profile of the DNA mixture (Bieber et al, 2016 and Semaan et al, 2020)
Interpretation of Two-Males Mixture: In most of the genetic loci, the DNA profiling of certain samples obtained expressed more than two peaks, confirming the existence in each sample of two contributors
Summary
Samples recovered for DNA analysis in a forensic crime scene often consist of mixtures of cells that may belong to the suspect, victim, and an infinite number of additional persons. Samples are often enriched with imbalanced mixtures of epithelial cells and sperm in sexual assault cases, with an excess of the victim's content, resulting in an unfavorable male to female DNA ratio. It is not possible to detect the male autosomal DNA portion of the mixture beyond the 1:10 to 1:20 ratio of male: female DNA (Vuichard et al, 2011) This is basically due to rivalry during PCR amplification for the primers, which contributes to the main component of the mixture being preferentially amplified. Differential DNA extraction, which does not require expensive equipment and is quickly achieved, is used by most forensic laboratories This method involves a mild step of cell lysis that allows an epithelial cell fraction enriched with DNA from the epithelial cells and leukocytes of the female to be recovered. The purpose of this study is to distinguish between samples collected from crime scenes whether they contain a mixture of DNA profiles and to study the contents of this genetic mixture and how genetic information can be extracted from it by separating profiles
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