SNPid

SNPid, or SNP identifier, is a unique label assigned to a single nucleotide polymorphism in public genetic variation databases. The most widely used SNP identifiers come from dbSNP, a repository maintained by the National Center for Biotechnology Information (NCBI). In this system, SNPs are labeled with rs numbers, such as rs123456, providing a stable reference that is independent of exact chromosomal coordinates.

A SNP record links the identifier to cross-referenced data: the genomic location in reference genome builds (for example GRCh37 or GRCh38), the reference and alternate alleles, allele frequencies in populations, and functional annotations (such as whether the variant is intronic, exonic, synonymous, or missense). This information enables researchers to interpret the potential biological impact of the variant and to compare findings across studies.

SNP identifiers facilitate data integration across studies and databases. However, coordinates can be updated as genome assemblies are revised; rsIDs are generally stable, but mappings to genome builds and allele representations can change with new evidence. Some SNPs have multiple representations or are grouped in linkage disequilibrium blocks, and not all identified variants have rsIDs, particularly rare or novel variants discovered outside well-curated catalogs.

In practice, SNPid is used in genetic association studies, imputation, sequencing reports, and annotation pipelines, serving as a canonical reference for communicating results. Researchers typically report the rs number along with the genome build version to ensure reproducibility. See also dbSNP and rs numbers as related concepts.