On 12 May 1984, a team led by British geneticist Alec Jeffreys published the first description of a technique that identified highly variable regions of human DNA and produced individual-specific banding patterns—an approach that would soon be called DNA fingerprinting or DNA profiling. The discovery emerged from fundamental research into repeated sequences in the genome and their use as markers for heredity and forensic identification. Background In the late 1970s and early 1980s, molecular genetics advanced rapidly: restriction enzymes, Southern blotting, and radioactive or chemiluminescent probes allowed researchers to detect specific DNA fragments. Jeffreys, working at the University of Leicester, was studying regions of the genome with tandemly repeated sequences—later termed minisatellites—that showed high variability in repeat number between individuals. By using probes that hybridized to these repeat sequences, his team observed multilocus patterns of bands on autoradiographs that differed from person to person. The method described Jeffreys and colleagues combined restriction enzyme digestion of genomic DNA with gel electrophoresis, transfer to a membrane (Southern blotting), and hybridization with probes complementary to repeat-rich regions. The resulting pattern of bands—reflecting fragments of different lengths produced by variable numbers and arrangements of repeats—was reproducible for an individual and inherited in families, but varied markedly between unrelated people. This multilocus banding pattern provided a means to distinguish individuals based on their DNA. Immediate implications and early uses Although the initial report focused on the method’s potential for studying human genetics and kinship, its forensic and identification applications were quickly recognized. Within a year of the publication, Jeffreys’ technique was used in a famous 1985 immigration case and in 1986 to help resolve a UK double murder investigation; those early forensic deployments popularized the term DNA fingerprinting. The method also proved valuable for paternity testing, population genetics, and studying genetic diversity. Technical evolution and legacy The original DNA fingerprinting technique relied on multilocus probes and autoradiographic band patterns. Over the following decade, the field moved toward single-locus probes and polymerase chain reaction (PCR)-based methods that targeted short tandem repeats (STRs), offering higher sensitivity, simpler interpretation, and compatibility with degraded samples. By the 1990s, standardized STR loci and databases became the foundation of modern forensic DNA profiling. Jeffreys’ 1984 work is widely recognized as the conceptual and technical origin of DNA fingerprinting. While subsequent methods refined and replaced aspects of the original protocol, the core insight—that variable repetitive DNA could serve as a powerful, individual-specific marker—remains a cornerstone of genetic identification. The discovery also prompted ethical, legal, and privacy debates that continue as DNA profiling technology and databases have expanded. Notes on sources and attribution The summary here is based on historical accounts and the scientific record of Alec Jeffreys’ work in the early 1980s. The specific date provided corresponds to the timeframe when Jeffreys first reported and publicized the technique; readers seeking primary sources should consult Jeffreys’ original publications and contemporaneous scientific literature for full experimental detail and context.