DNA fingerprinting

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.

Synonym(s): DNA profiling, DNA typing

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 fingerprinting

n.

See DNA profiling.

DNA fingerprinting

a technique for comparing the nucleotide sequences of fragments of DNA from different sources. The fragments are obtained by treating the DNA with various endonucleases, enzymes that break DNA strands at specific sites. There is a chance of 1 in 30 billion that two persons who are not monozygotic twins would have identical DNA fingerprints. To resolve the complexities of the process, short, tandemly repeated, highly specific "minisatellite" genomic sequences are used. A wild-type M13 bacteriophage that identifies the differences is confined to two clusters of 15-base-pair repeats in the protein III gene of the bacteriophage. The specificity of the probe makes it applicable to questions of forensic science.

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.

DNA fin·ger·print·ing

(fing'gĕr-print'ing)

A technique used to compare people using molecular genotyping. DNA is isolated from a specific person, digested, and fractionated according to size. A Southern hybridization with a radiolabeled repetitive DNA probe provides an autoradiographic pattern unique to that person. DNA fingerprinting offers a statistical basis for evaluating the probability that samples of blood, hair, semen, or tissue have originated from a given individual.

DNA fingerprinting

The recording of a pattern of bands on transparent film, corresponding to the unique sequence of regions in the DNA (core sequences) of an individual. DNA fragments, obtained from a DNA sample by cutting it with restriction enzymes, are separated on a sheet of gel by ELECTROPHORESIS. The fragments are then denatured into single strands and the gel is blotted onto a membrane of nylon or nitrocellulose which fixes the fragments in place. Radioactive probes, complementary to the core sequences, are then added. These bind to any fragment containing the core sequence. The membrane is laid on a sheet of photographic film and a pattern of bands is produced by the action of the radiation. The arrangement of the banding pattern is unique to each unrelated person but parents and their offspring have common features. Patterns from different individuals, or from different samples from the same individual can be compared. The method can be used as a means of positive identification or of paternity testing. Only a tiny sample of blood, semen or of any body tissue is needed to provide the DNA.

DNA fingerprinting

see FINGERPRINTING.

DNA fin·ger·print·ing

(fing'gĕr-print'ing)

A technique used to compare people using molecular genotyping.