NCBI GenBank
GenBank® is the NIH genetic sequence database, an annotated collection of all publicly available DNA sequences (Nucleic Acids Research 2004 Jan 1;32(1):23-6). There are approximately 37,893,844,733 bases in 32,549,400 sequence records as of February 2004 (see GenBank growth statistics). As an example, you may view the record for a Saccharomyces cerevisiae gene. The taxonomy is not considered authoritative, but a useful guide. Contains many links to other taxonomic resources.
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NCBI GenBank