Tools for successful DNA typing of exhumed bodies
What is exhumation?
Exhumation is the process by which the remains of the deceased are exhumed from the burial site; this can be done for cremated remains and buried bodies. Simply put, an exhumed body is a buried corpse that has been excavated after years or a certain period, either for legal purposes or to move the grave. Generally, exhumation is confused with the recovery of illegally buried bodies. In any case, when a person has been killed and buried illegally or secretly in order to destroy all evidence related to the murder, the recovery of these bodies is not considered an exhumation. It is only when the proper burial is legally performed with all the rituals that the exhumation can then be applicable.
Does exhumation require legal authorization?
To perform an exhumation, contact a licensed professional to perform such procedures when the reason for the exhumation of the deceased is detailed. In India, corpses are only exhumed with the written order of the first class magistrate under article 176 of the Code of Criminal Procedure and the police under article 174 of the Code of Criminal Procedure can recover the body buried illegally. The coroner’s system does not exist in India but in the countries where it is applicable, it is the coroners who generally allow the exhumation.
Reasons for exhumation
Exhumations are very rare and can be traumatic for the family or loved ones involved. He suggests consulting all family members before proceeding. There are various reasons for carrying out an exhumation such as the police investigation, DNA tests, the choice of the family or in order to transport the deceased to his country of origin; it takes a long time to read the permission and it’s all about the emotions attached. Exhumation is essential in certain cases where, subsequently, new facts are revealed showing a criminal act due to which the autopsy or other findings become necessary to establish the cause of death or to resolve the case. Here, the samples in question are taken from the deceased and this is when forensic medicine comes in. In such cases, DNA profiling or typing plays a vital role for individualization and identification in the event of unknown bodies and mass disasters. Sometimes in degraded bodies, bones are the only accessible source of DNA and sometimes teeth too.
DNA extraction methods
New extraction methods are always being researched and improved. Short Tandem Repeat Analysis (STR) primarily performed for personal identification. Nuclear DNA from bones at different stages of degradation is isolated using three methods:
Organic phenol chloroform extraction method.
Extraction of DNA from crystalline aggregates provides much better removal of inhibitors and is a good method of choice when determining the identity of exhumed bodies is required.
Extraction by the method of total demineralization, which is said to be the best method in most cases of extracting DNA from bone although it does not provide pure DNA and these extracted DNAs are then compared to the using the PCR amplification method.
The possibility of DNA extraction from bones and teeth exposed over time to various environmental effects becomes a valuable tool for the identification of missing persons and unknown remains. There are different steps for the identification of human skeletal remains which consist of preparation, pulverization, DNA extraction, quality control, PCR, DNA profiling and database. For human identification, it is very important to have DNA manufacturers, which exhibit the greatest possible variation or a number of less polymorphic markers, which can combine in order to obtain the ability to distinguish the samples obtained. As a result, forensic samples are often difficult to amplify by PCR, as the DNA in the sample can be severely degraded.
DNA typing tools
Restriction Fragment Length Polymorphism (RFLP):
Normal variations can often occur in the DNA sequence of coding and non-coding regions, as sequence polymorphism and length polymorphism are the two main forms of DNA variation. Decalcification tends to improve DNA typing success and due to the high degree of polymorphism exhibited by STR loci and the sensitivity of PCR amplification of STR alleles and all of these new clinical testing procedures benefit greatly from the STR typing. Often used DNA typing methods are RFPL and PCR techniques. Restriction Fragment Length Polymorphism (RFLP). RFLP analysis was the first technique used in forensics for DNA typing. This technique shows variations in homologous DNA sequences, such as to distinguish individuals and populations or species or to locate the locations of genes within a sequence.
Polymerase chain reaction (PCR):
Polymerase chain reaction (PCR). PCR-based STR analysis is now a more modern approach to DNA typing. This DNA profiling method used today relies on PCR which uses short tandem repeats (STR) after DNA extraction and amplification by PCR, then genotyping performed, giving the results accurately. Sequence polymorphism results from differences in the base sequence at a particular locus. Basically, the locus is a specific location on a DNA molecule and length polymorphism results from differences in DNA length at a particular locus where differences in DNA length are due to variations in the number of times ‘a certain base sequence is repeated. The number of times a certain sequence repeats at a specific locus can often vary from individual to individual, this locus which has a repeat unit of nine to ninety-eight bases is called a repeat locus. in tandem with variable number (VNTR). Therefore, loci that have a repeat unit of only two to seven bases are called short tandem repeats (STRs) or microsatellites.
Nuclear DNA typing can also be done using an AmpflSTR Profiler kit and mitochondrial DNA typing of hypervariable regions such as HV1 and HV2 in a controlled region are both done with powder samples. decalcified and untreated bones that are extracted and aAn alternative to these markers is the use of single nucleotide polymorphisms (SNPs). Tools used specifically for SNP typing, which is multiplex PCR-based amplification followed by simultaneous primer extension detection (PEX), are further analyzed by laser-assisted desorption time-of-flight mass spectrometry. by matrix (MALDI-TOF MS). These tools and techniques have a particular advantage in the analysis of degraded or poor samples.
DNA typing often involves specimens containing degraded material, in lesser quantities, contaminated or from several unknown sources. Sometimes it cannot be repeated, due to the smaller quantity and the limitation of the sample size. Despite the challenges, we believe that it is possible to develop reliable forensic DNA typing systems in the future, as they progress rapidly. RFLP– input-based typing methods continue to be refined and improved in the coming times, PCR typing methods and tools generally used in some court cases, and other tools and techniques are developing in scientific and commercial research laboratories. DNA typing tools and methods will continue to be replaced by increasingly sophisticated approaches in the times to come.
- Alonso, A. (2001, June). DNA typing from skeletal remains: evaluation of multiplex and megaplex STR systems on DNA isolated from bone and tooth samples. PubMed. https://pubmed.ncbi.nlm.nih.gov/11387635/
- Alonso, et al., A. (2001). DNA typing from skeletal remains: evaluation of multiplex and megaplex STR systems on DNA isolated from bone and tooth samples. Croatian Medical Journal. https://www.promega.com/-/media/files/resources/profiles-in-dna/403/dna-typing-from-skeletal-remains-evaluation-of-multiplex-and-megaplex-str-systems. pdf? la = fr
- Comparison of three methods of DNA extraction from human bones with different degrees of degradation. (2012). PubMed Central (PMC). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3254873/
- DNA extraction methods. (2012, January 1). ScienceDirect. https://www.sciencedirect.com/science/article/pii/B9780123745132000026
- DNA typing | Encyclopédie.com. (2021, February 29). ENCYCLOpedia.com. https://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/dna-typing-0
- Identification by DNA analysis in criminal and family investigations. (January 1, 2010, 2010). ScienceDirect. https://www.sciencedirect.com/science/article/pii/B9780123694287000318
- PCR amplification: capabilities and precautions. (2012, January 1). ScienceDirect. https://www.sciencedirect.com/science/article/pii/B978012374513200004X
- Petkovski, E. (2005, May). SNP and MALDI-TOF MS: tools for DNA typing in forensic paternity testing and anthropology. PubMed. https://pubmed.ncbi.nlm.nih.gov/15932083/
- Short Tandem Rehearsal Rooms and Kits (STR). (2012, January 1). ScienceDirect. https://www.sciencedirect.com/science/article/pii/B9780123745132000051
- Stanleys, E. (2019, January 30). Exhumation guide. Exhumation services of the Rowland brothers. https://rbexhumations.com/exhumation-guide/
- Tahir, MA (2000, July 1). DNA typing of samples for Polymarker, DQA1 and nine STR loci from exhumed human body after 27 years. ASTM International. https://www.astm.org/DIGITAL_LIBRARY/JOURNALS/FORENSIC/PAGES/JFS14795J.htm