DNA typing


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DNA fin·ger·print·ing

a technique used to compare individuals by molecular genotyping. DNA isolated from a biologic specimen is digested and fractionated. Southern hybridization with a radiolabeled repetitive DNA provides an autoradiographic pattern unique to the individual.

DNA fingerprinting depends on the detection of distinctive DNA sequences in human cellular material (skin, hair, blood, semen). The principal applications of this technique, all of which are based on the premise that no two people have exactly the same genetic makeup, are in determining paternity and maternity, identifying human remains, and matching biologic material left at a crime scene with that of a suspect. The most distinctive features of a person's genome are not the genes themselves but variations in the length and distribution of nongenetic material between gene loci. Although these do not transmit genetic information, they are highly consistent within the cells of each person and highly variable from one person to another. Distinctive nucleotide sequences that are most useful in DNA fingerprinting are variable number tandem repeats (VNTRs) and short tandem repeats (STRs). In DNA fingerprinting, the specimen is split into nucleotide fragments by treatment with restriction enzymes and then subjected to gel electrophoresis so as to yield a characteristic pattern of banding. Radioactive probes, composed of short nucleotide sequences (10-15 base pairs for VNTRs, 3-4 pairs for STRs), then identify sites of tandem repeats and hybridize with them. Comparing the results from two or more DNA sources reveals their degree of relatedness. The U.S. Crime Act of 1994 and similar laws in other countries have mandated archival storage of DNA fingerprints of those convicted of certain crimes.

DNA typing

The analysis of short, highly specific, tandem-repeated—or hypervariable— genomic sequences, minisatellites known as variable number of tandem repeats (VNTRs), to detect the degree of relatedness to another sequence of oligonucleotides. This method of isolating and visualising of sequences of DNA was developed in 1984 by Alec Jeffreys, who identified minisatellites that do not contribute to gene function but are repeated in the genes and elsewhere in a DNA sample, thus providing highly specific information about that organism or person.
References in periodicals archive ?
Yet despite these immediate differences, the authors' diverging attitudes toward DNA typing remain fairly evident.
Yet DNA typing is only one of many ways in which DNA analyses are used in forensic investigations.
Development Agency (NWDA) to further enable development of a ground-breaking new method for DNA typing.
31) However, in two New York cases, (32) "the defense actually called witnesses to challenge prosecution claims about the validity and reliability of [a] DNA typing technique.
LCN DNA typing has been defined as "the analysis of any results below the stochastic threshold for normal interpretation," (6) using samples of microscopic amounts of DNA for analysis often as little as 100-200 pg input DNA.
Subsequent DNA typing indicated that none were the strain responsible for Legionnaires' disease.
The introduction of blood typing, and then DNA typing in 2001, has caused a sea change in the accuracy of thoroughbred record-keeping, says Mercer.
Shaler tells of difficulty in collecting the samples, keeping them from decomposing, and then DNA typing the material.
Microbial DNA typing by automated repetitive-sequence-based PCR.
DNA typing from skeletal remains: evaluation of multiplex and megaplex STR systems on DNA isolated from bone and teeth samples.