DNA Typing Analysis

Abstract

DNA typing analysis consists in generating and interpreting allelic profiles for the purpose of identifying an individual, a representative from a given group or species, or to determine the origin/provenance of biological material such as cells, clinical specimens, and forensic evidence. The process capitalizes on length differences or sequence variations (collectively referred to as polymorphisms) associated with discrete regions within the genomes of living organisms. These genetic differences are examined using a variety of DNA profiling strategies that utilize different modes of detection to reveal the polymorphic nature of the target DNA segments. The choice of method adopted is largely dictated by the nature, quantity, and physical state of the sample to be identified. Each of these considerations, in addition to the current state of knowledge regarding the sequence, structure, and organization of an organism's nuclear and organelle genomes, will also determine what type of polymorphisms can be surveyed. Polymorphic allele patterns can be represented as bar code–like profiles, peaks on tracings, photographic bars or dots on X-ray films, or colored spots on solid supports or computer monitors. DNA typing can be applied to any biological material that contains DNA such that current applications reach across every taxonomic kingdom. DNA typing analysis is particularly powerful because no two individuals or strains, with the exception of genetically identical twins and clones, share the same allele complement for multiple polymorphic loci. In addition, with the advent of DNA typing strategies based on the polymerase chain reaction (PCR), investigators have advanced beyond conventional restriction fragment length polymorphism (RFLP) analysis and can carry out reliable, accurate, precise, and sensitive identifications from only minute quantities of starting biological material. This, coupled with the surprising chemical stability and longevity of DNA, has had a major impact in forensic science for the resolution of violent crimes or the identification of human skeletal remains from the scenes of mass disasters. Today, DNA typing analysis is employed in almost every discipline under the biological sciences. It continues to prove instrumental to studies on human origins and diversity, in clinical medicine to resolve the identity of specimens, ascertain the provenance of transplantable tissues and organs, and expedite the identification of viral and microbial pathogens, and in guiding the manner in which animal, plant, and insect breeding programs are being conducted and followed. This article describes the general principles underlying DNA typing analysis, summarizes and compares currently available methods for specimen identification, and provides an overview of applications in the field of forensics and the biological sciences. Keywords: AmpFLP (Amplified Fragment Length Polymorphism); AP-PCR (Arbitrarily Primed Polymerase Chain Reaction); DAF (DNA Amplification Fingerprinting); ISSR (Inter Simple Sequence Repeat); Microsatellites and Minisatellites; RAPD (Random Amplified Polymorphic DNA); Sequencing; SNP (Single-nucleotide Polymorphism); STR (Short Tandem Repeat); VNTR (Variable Number of Tandem Repeats)