GenBank: An annotated collection of all publicly available nucleotide and amino acid sequences. EST database: A collection of expressed sequence tags, or short, single-pass sequence reads from mRNA (cDNA). GSS database: A database of genome survey sequences, or short, single pass genomic sequences. HTG database: A collection of high throughput genome sequences from large-scale genome sequencing centers; including unfinished and finished sequences. SNPs database: A central repository for both single base nucleotide substitutions and short deletion and insertion polymorphisms. RefSeq: A database of non-redundant reference sequences standards, including genomic DNA contigs, mRNAs and proteins for known genes. Multiple collaborations, both within NCBI and with external groups, support our data-gathering efforts. STS database: A database of sequence tagged sites; or short sequences that are operationally unique in the genome. UniSTS: A unified, non-redundant view of sequence tagged sites (STSs). UniGene: A collection of ESTs and full-length mRNA sequences organized into clusters, each representing a unique known or putative human gene annotated with mapping and expression information and cross-references to other sources.