Agarose FP

DNA polymorphisms are widely used to determine paternity, kinship, identification of human remains
and the genetic base of several illnesses.
Identification with DNA or “genetic fingerprint” is based on the study of a series of DNA fragments present in all
individuals and these can be highly variable or polymorphic among each other (VNTR).
The analysis of a determined number of these sequences or fragments of DNA allows an individual to be identified with a
probability of success close to 100%.
In order to analyze these DNA polymorphisms, forensic Identification laboratories use a series of techniques which are
continuously evolving, achieving increasing positive identifications by means of DNA.
Forensic Hemogenetics has existed since the beginning of the 20th century, when Karl Landsteiner put forward the ABO
blood group system and Von Durgen and Hirschfeld explained their hereditary transmission. The objective of this science
was the genetic identification in criminal investigations and biological studies on paternity testing. Initially investigations
centered on the study of red cell antigens (ABO system, Rh, MN), serum proteins, erythrocyte enzymes and the HLA
system. By studying these markers, an individual could be included or excluded as a possible suspect by possessing a
genetic combination the same as, or different to, the biological trace evidence found at the crime scene.
By mid-century, owing to the discovery of DNA and its structure, and the subsequent advancement in techniques for
analyzing the DNA molecule, Forensic Hemogenetics evolved considerably, to the point where today we speak of a new
subspecialty within Forensic Medicine: Forensic Genetics. This science studies certain areas of DNA which vary from
individual to individual, i.e. it studies polymorphic regions of DNA. Therefore, by studying a determined number of
polymorphic regions, the probability that two individuals are genetically identical is almost nil (except in the case of
In 1985, Alec J. Jeffreys discovered RFLPs (restriction fragment length polymorphism). Since DNA is treated with
restriction enzymes, they generate variable length fragments. Subsequent studies undertaken by Jeffreys himself
demonstrated that the difference in size of these fragments was due to these regions consisting of a determined number
of repetitions in tandem of a central sequence, which varied in some individuals to others.
The first DNA polymorphic locus was discovered by Wyman and White in 1980 using an arbitrary DNA probe. In this way
they observed fragments of more than 15 different lengths in a small sample of individuals. These hypervariable loci
consisted of repetitions in tandem of a sequence of oligonucleotides (11 a 60 pb), in such a way that the different lengths
of the generated fragments depended on the number of these repetitions and they called them VNTR (“Variable Number
of Tandem Repeat”). Following the Discovery of the first VNTRs it was thought that these could be applied to forensic medicine and substitute
traditional labelling.
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