In 1998, Francis Collins, then director of the US National Human Genome Research Institute, or NHGRI, announced the creation of a tool for discovering genetic variation called the DNA Polymorphism Discovery Resource, or PDR. The PDR was a collection of cell lines housed in a central biobank. Scientists made those cell lines from blood samples they obtained from 450 US residents of diverse ancestry. They created the PDR to help researchers discover a particular type of genetic variation called single nucleotide polymorphisms, or SNPs. A SNP is a variation in a single letter of DNA at a particular location along a DNA molecule. SNPs can serve as markers when scientists look for associations between specific DNA regions and human traits, including common diseases like heart disease and cancer. Although as of 2024 the PDR is no longer available, it enabled scientists to identify more than a million SNPs spread over the whole human genome, a necessary precursor to studies aimed at identifying genetic variation that contributes to health and illness.