Authors
Dr. Nadeem Mubarik
Abstract
DNA typing is emerging as an important tool for boosting criminal justice delivery system of the whole world. The technique has made tremendous progress in the recent past. With the progress of time all possible efforts have been made to develop better multiplex systems to cater with new challenges. Efforts are made to include the impact of linkage and linkage disequilibrium in calculating likelihood ratios when dealing with close relations. Efforts are also underway to increase the strength of databases by making intensive and extensive studies covering different populations of the world. Extensive research is being carried out to get better information regarding the mechanism and marker specific mutation rates in STRs. Computer based models are designed to get better insights in calculating the impact of all the factors that have a potential to disturb the likelihood calculations. This chapter is designed to acquaint the reader about all these concepts. Keywords: STR typing, Linkage, Mutation, Recombination
Introduction
The experiments performed by Gregor Johnn Mendel during 1860’s on the garden pea plant laid a foundation of understanding the basic principles of genetics, commonly known as Medalian genetics. Based on simple pedigree analysis it was made clear that the characters are inherited from parents to their off springs. During his studies, Mendel postulated some basic principles like Dominance, Segregation and independent assortment of characters. In the modern era, the study of inheritance performed at the molecular level is based on some seemingly esoteric concepts, which of course need to be resolved at the outset so that the concept is understood as a whole. The human genome is composed of millions of nucleotides and only a small portion of it is utilized as a tool in differentiating individuals from each other, first done by Sir Aliec Jaffrey in 1984 (Jeffreys et al., 1985). The technique however remained less appreciated and was mostly employed in demystifying the genetic disorders due to malfunction in some of the genes in the close proximity of the repetitive sequences. Soon after the value of genetic diversity among these repetitive sequences was recognized, more and more research started focusing on recognizing the potential hotspots for better variability and stability. The invention of Polymerase Chain Reaction in 1985 by Kary B. Mullis proved a milestone as the technique was based on a powerful concept of generating multiple copied from the desired segments of DNA. The invention was unequivocally a major breakthrough to defeat the constraints of low template DNA, met mostly in forensic samples. The quest of designing better and more reliable hotspots having better polymorphic characters and greater stability, more genetic markers were added in order to increase the discrimination power. Consequently, a huge number of markers have already found there place in various multiplex kits. Even the markers from same chromosome, having impact of linkage are being selected which of course are going to actually disturb the calculated value of evidence, if the linkage factor is ignored. In this chapter we shall try to evaluate the effect of two important concepts –Linkage and Mutations on STR typing and interpretation of results. However, before going in to the discussing precisely, there are certain basic concepts which need to be understood first especially for the beginners.
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| APA Style | Mubarik, Dr. N. (2024). Impact of Linkage and Mutations on STR Typing and Interpretation of Results. Academic Journal of Forensic Sciences, 07(01), 18–28. |
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