Sanger sequencing is a laboratory method that scientists use to determine the sequence of nucleotides within a piece of deoxyribonucleic acid, or DNA. Frederick Sanger, who studied biochemistry in the United Kingdom, and colleagues developed the technique in 1977. Sanger sequencing was one of the first methods to sequence long stretches of DNA accurately, allowing researchers to collect and analyze large amounts of genetic data. The technique uses modified nucleotides that terminate DNA synthesis at specific points, which results in fragments of varying lengths that researchers sort to determine the sequence of nucleotides. Sanger sequencing was one of the most widely used sequencing methods for thirty years after its creation and facilitated early genomic sequencing projects, such as the Human Genome Project, or HGP. As of 2025, Sanger sequencing remains a common technique despite the advent of newer sequencing technologies and plays a role in clinical settings and genetic counseling, a service that provides information on genetic conditions to people and their families.