Serology and DNA Essay

Blood Structure Analysis

As a rule, almost every genotypic examination begins with the determination of the presence of biological material on the carrier object, submitted for examination. Modern science has developed many primary and evidence-based methods for identifying blood, saliva, sperm, urine, and other tissues and body fluids. The fluid chosen for discussion is blood.

There are two groups of blood detection methods: preliminary, which only suggest the presence of blood in the object and are used mainly during the inspection of the scene of the incident, and evidentiary, which confirm the presence of blood on the carrier. According to Li et al (2011), evidence-based methods for the origin of bloodstains are based on the detection of hemoglobin and its derivatives, as well as substances characteristic only of blood.Serology and DNA Essay.  For instance, the spectral method is based on the ability of hemoglobin and its derivatives (methemoglobin, carboxyhemoglobin, hematoporphyrin) to absorb light waves of a certain length and form characteristic absorption spectra. According to Karger et al (2008), detection of the hemoglobin spectrum proves the presence of blood in the test object. There is also microspectral method (establishing blood in a microquantity of a substance) and emission spectral analysis (used in case of deep blood destruction, for example, during charring or rotting).

In addition, it can be said that the thin-layer chromatography method allows to obtain a positive result even in cases where conventional methods of determining the presence of blood are ineffective. The principle of the method lies in the fact that the solvent (ammonia solution and butanol), passing through samples cut from the objects of study and fixed on chromatographic paper, decomposes the blood into components, which then should be manifested properly. After carrying out certain procedures, a change in the color of the pigment site proves the blood origin of the spot. To identify blood in contaminated and old stains, as well as bloodstains on tissues subjected to washing, the method of direct radial microchromatography on paper is used.

Thus, modern science and practice have developed many methods for detecting biological fluids on objects – carriers. In order to properly conduct such a research, it is necessary not only to have special knowledge in various fields of science: forensic science, the criminal process, physics, chemistry, biology and other sciences, but also be able to competently apply them in practice.

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References

Li, B., et al. (2011). “The estimation of the age of a blood stain using reflectance spectroscopy with a microspectrophotometer, spectral pre-processing and linear discriminant analysis.” Forensic Sci Int., 212 (1-3).

Karger, B., et al. (2008). “Bloodstain pattern analysis–casework experience.” Forensic Sci Int., 181 (1-3). Serology and DNA Essay.

Crime Laboratories routinely process evidence from criminal cases for the presence of biological fluids such as blood, semen, and saliva in order to obtain DNA profiles. Forensic Biology encompasses both Forensic Serology and DNA testing. Prior to examination, it is important for the forensic scientist to evaluate the type of crime and the samples submitted so that the evidence can be processed in the proper order for the type of testing needed. Typically, evidence will be analyzed using a mix of presumptive and confirmatory tests to determine the presence of biological stains prior to DNA analysis, although this may not always be feasible when the amount of sample is limited. These Forensic Serology tests assist the analyst in determining which samples will go forward to DNA testing. Forensic DNA testing in most crime laboratories in the United States is done using short tandem repeat (STR) analysis of the 13 core CODIS STR loci. This chapter introduces routine serology procedures, the DNA testing process, the interpretation of DNA profiles, and the national DNA database, CODIS.

In the forensic community, serology and DNA analyses are closely related. In fact, in many laboratories they are included within the same personnel section. In the forensic crime laboratory, “serology analysis” refers to the screening of evidence for bodily fluids, whereas “DNA analysis” refers to the efforts to individualize bodily fluids to a specific person. In most cases, bodily fluid identification is performed on evidentiary items before DNA analysis is attempted. Depending on the qualifications of laboratory personnel, analysts can be trained to perform either serology or DNA analysis or can be trained in both disciplines. Although serology procedures have been employed for most of the 20th century and the techniques have essentially remained unchanged, DNA has emerged in the forensic realm within the last two decades and its applications and technology are continuously developing.

Keywords: DNA identification; DNA typing; Deoxyribonucleic acid (DNA); forensic serology; genetic markers; human leukocyte antigen (HLA) DQ-α; immunology; urine. Serology and DNA Essay.