DNA typing is the scientific process by which normally occurring
variations in DNA are detected. Identification and determination of paternity are the two major applications of genetic identity testing. In contrast to clinical genetics, forensic DNA typing examines the properties of noncoding loci spread over the entire human genome. Since noncoding loci are not expressed, DNA typing does not reveal any information about an individual, such as presence of a heritable genetic disease, but rather the mere identity or relatedness of the individual to another (1). Many countries are now in the process of collecting and typing DNA from convicted offenders and storing the genotypes in centralized searchable databases. These databases will eventually include the DNA profiles of millions of individuals and will make it possible to link crime scenes to suspects. In order to standardize these databases, countries have selected standard sets of STR (short tandem repeat) loci to use. STR loci consist of short, repetitive sequence elements 3-7 base pairs in length (2-5). These repeats are well distributed throughout the human genome and are a rich source of highly polymorphic markers, which can be detected using PCR (6-9). Alleles of STR loci are differentiated by the number of copies of the repeat sequence contained within the amplified region and are distinguished from one another using radioactive, silver stain or fluorescence detection following electrophoretic separation.
In the United States, the FBI has established the Combined DNA Indexing System (CODIS) and identified 13 core STR loci that must be typed prior to searching or submitting samples (10-12). In Europe, ENFSI (European Network of Forensic Science Institutes) has selected seven loci, and Interpol has established a set of four loci as a pan-European standard. In Latin America, GITAD (Grupo Iberoamericano de Trabajo en Analisis de DNA) has selected six STR loci for inclusion in their database system (13).
DNA typing technology has advanced greatly, and Promega has led the way with its Multiplex STR Systems, including the recently released PowerPlex™ 16 System. Promega has also led the way with its unprecedented decision to disclose proprietary information. Those who are interested in the advancements in the field of human identification will be attending the 11th International Symposium on Human Identification.
References 1. Benecke, M. (1997) Naturwissenschaften 84, 181. PowerPlex™ 16 - Promega's Decision - What is DNA Typing?
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Each person's DNA typing pattern is
different. This property is the fundamental basis for determining whether two people are
related to each other. Similarly, DNA typing has become the basis of forensic analysis,
which is the matching of suspects to biological crime scene evidence. DNA typing results
are used by attorneys, judges, law enforcement officials, physicians and even private
individuals.
