Forensic Identification by Using Insertion-deletion Polymorphisms

Forensic science is basically the determination of the human identity. With advances in science and technology and the availability of DNA profiling, it is possible now to determine the identity even in decomposed and mutilated bodies and even with parts of a body as trivial as a hair or a drop of a blood. Methods and materials: Short tandem repeat polymorphism (STRP) genotyping and single nucleotide polymorphism (SNP) are the wellknown DNA profiling methods used in the forensic field, but having drawbacks like need of big amplicons, having higher mutation rates and requiring complicated procedures, and being expensive respectively. Insertion Deletion polymorphism (INDEL) is a natural genetic variation due to the insertion or deletion of nucleotide in the human genome, and INDEL typing requires smaller DNA samples and are the most abundant variations in the human genome. INDELs are analysed with a simple fluorescent PCT followed by capillary electrophoresis, at present Qiagen Investigator DIPplex® kit of 30 INDELs and a 38-INDEL multiplex assays are available. Objectives: INDEL typing is useful in forensic genetics, population genetic studies, and medical genetics as in human and kinship analysis. With the advent of INDEL-STP typing technique an autosomal DNA profile of a minor donor is also plausible. Conclusion: Personalized therapy is possible with INDEL typing as it is helpful in determining the source of genetic diseases. This paper explores the application of INDELs in forensic identification. Address for correspondence: Dr. Vasudeva Murthy.C.R. Department of Pathology, International Medical University, Kuala Lumpur, Malaysia Telephone: 03-2727 7430 Fax: +603-8656 7229 / 8656 8018 E-mail: [email protected] INTRODUCTION Forensic science is the application of science to legal problems; that is, science applied to criminal cases, national security, as well as civil and administrative matters (Bush 2015). Mostly, forensic science works on criminal cases, such as homicides and sexual assaults; yet, forensic science is also applied to civil matters, for example, disputed paternity and product failures (Dobash and Dobash 2015). In term of criminal case, forensic science is applied to investigate the corpus delicti, to identify substances and individuals, to provide investigative clues, to develop linkages in the case as well as to support or disprove statements by witnesses, victims or suspects (Sefanyetso 2009). In fact, forensic identification or human identification can be indeed challenging in most cases. Basically, by using old methods, an individual can be identified by his morphological characteristics, fingerprint, teeth, body tissues, body fluid, bone, tattoo or body piercing (Vij 2011; Shepherd 2003). Unfortunately, these old methods display drawbacks and are inapt in the identification of victims of fire, explosion, air crash, or road accidents, when the body is incomplete, highly decomposed or skeletalised. Over decades, forensic scientists have been working diligently to invent new methods to overcome the obstacles in forensic identifications. As technology advanced, scientists have eventually invented DNA profiling as the latest strategy in forensic identification. Under DNA profiling, there are two common methods, namely short tandem repeat polymorphism (STRP) genotyping and single nucleotide polymorphism (SNP) genotyping, which are usually used for identification. STRs or short tandem repeats are tandemly repeated DNA segments with repeat lengths up to 6 bp and total lengths commonly less than 60 bp, in human genome (Hameed et al. 2014). On the other hand, SNPs or single nucleotide polymorphisms are the most abundant form of genetic variation in humans (Twyman 2013). Both STRPs and SNPs show natural variation in a population, and thus, can be genotyped and analysed for forensic identification. At present, STRP genotyping is known as the standard procedure in forensic identification, however, STRPs have high mutation rates and big amplicons are needed in STRP analysis, which makes 56 VASUDEVA MURTHY, LIM FUEY JIA VIJAYA PAUL SAMUEL ET AL. it inapplicable in deficiency cases (Schneider 2012). As an alternate method, SNP genotyping has covered the limitation of STRP genotyping method, as SNPs have low mutation rates and can be analysed with small amplicons (Pereira et al. 2012). Even so, SNP typing technique has its own limitation, for instance, complicated procedures and expensive, advanced technologies are all needed to genotype SNPs in human genome (Twyman 2013). With no doubt, the methods and technologies used for forensic identification are far from advances, making the identification even more challenging. To overcome these obstacles a new technique called the insertion deletion polymorphism (INDEL) typing which was discovered recently, can aid in identification even when very small amount of DNA sample is available in the crime scene. Furthermore, INDEL is one of the most abundant genetic variations in human genome, which is easier to be genotyped compared to STRP and SNP (Reid 2013). Besides its application on forensic genetics, INDEL typing is as well applicable in population studies and medical genetics (Børsting and Morling 2015). In this review, the methodology for the detection of INDELs, its applications as well as its advantages and disadvantages are highlighted.