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 ?
Balestrieri et al., "Estimation of European otter (Lutra lutra) population size by fecal DNA typing in southern Italy," Journal of Mammalogy, vol.
STR DNA Typing: Increased Sensitivity and Efficient Sample Consumption Using Reduced PCR Reaction Volumes.
Yet despite these immediate differences, the authors' diverging attitudes toward DNA typing remain fairly evident.
Few seriously doubt DNA typing's high reliability in determining whether any two isolated samples match.
Low to high resolution DNA typing is possible with this technique.
Development Agency (NWDA) to further enable development of a ground-breaking new method for DNA typing.
The utility of short tandem repeat loci beyond human identification: implications for development of new DNA typing systems.
Simpson case, Aronson demonstrates that "the debates over DNA profiling were essentially over when Simpson's criminal trial began in January 1995." (14) While doubts may persist concerning the criminal justice system, as evidenced by the Innocence Project's success in freeing over 200 wrongfully convicted people, (15) "DNA technology is no longer on trial; in fact, it has now been rather neatly integrated into the courtroom." (16) Indeed, the founders of the Innocence Project, Barry Scheck and Peter Neufeld, both of whom had been active in challenging the validity and reliability of DNA typing in Castro and Yee, are nowadays busy "instilling a kind of mythic power to DNA evidence" (17): Sometimes eyewitnesses make mistakes.
While the basics of crime detection and prosecution have remained fairly constant for centuries, the combination of DNA typing and computerized data-sharing is proving to be highly potent weapon in the crime fighter's arsenal.
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.