DNA fingerprinting is a molecular technique that creates a distinctive profile of an organism’s DNA by analyzing variations in repetitive nucleotide sequences. It relies on differences in variable number tandem repeats or short tandem repeats to distinguish between individuals, except identical twins.
Principle and Methodology
Developed in the 1980s by British geneticist Alec Jeffreys, DNA fingerprinting exploits natural variation in minisatellite or microsatellite regions that are not part of coding genes. The process typically begins with extraction of DNA from blood, saliva, or tissue. Restriction enzymes cut the DNA into fragments, which are separated by size using gel electrophoresis. Early methods such as restriction fragment length polymorphism (RFLP) used Southern blotting to transfer DNA fragments to a membrane and hybridize them with labeled probes targeting variable repeats. Modern approaches often amplify short tandem repeats by polymerase chain reaction (PCR) and analyze fragment lengths with capillary electrophoresis. Because these tandem repeats vary greatly among individuals, the resulting banding patterns or fragment-length profiles are highly specific. In microbiology and epidemiology, pulsed‑field gel electrophoresis and multilocus sequence typing are extensions of DNA fingerprinting that help trace bacterial and fungal strains during outbreaks. The technique has revolutionized forensic science, paternity testing, conservation genetics, and the authentication of biological samples. Despite its power, results can be compromised by degraded samples or contamination, so rigorous laboratory practice and statistical analysis are essential.
Forensic and Epidemiological Applications
By comparing the DNA fingerprints of crime‑scene samples with those of suspects, forensic investigators can confirm or exclude individuals with high confidence. Courts routinely admit DNA profiles as evidence, provided that laboratory methods and population statistics are sound. In paternity and kinship testing, matching of child and parental alleles at multiple loci can establish biological relationships. Epidemiologists use DNA fingerprinting to monitor foodborne outbreaks by identifying indistinguishable patterns among bacterial isolates, allowing rapid tracing of contamination sources. Wildlife biologists employ microsatellite profiling to study genetic diversity and to enforce laws against illegal trade. The technology also assists in verifying the origin of cell lines and identifying mislabeled specimens in research laboratories.
A precise DNA fingerprint serves as a unique identifier for organisms, making it invaluable in law enforcement, medicine, and biology. Advances in PCR and sequencing continue to enhance sensitivity and reduce the amount of DNA needed. However, careful interpretation and quality control remain vital to avoid false associations or misidentification.
Related Terms: Genetic profiling, Restriction fragment length polymorphism, Minisatellite, Microsatellite, Gel electrophoresis