- Expressed Sequence Tags (ESTs) are essentially Sequence Tagged Sites (STS) that are represented in mRNA. They are derived as 300-500 bp single-pass mRNA sequence reads from many of the genes expressed in a given tissue and/or at a given developmental stage. They represent a snapshot of gene expression in a given place or time.
Definition from: NCI Thesaurus via Unified Medical Language System at the National Library of Medicine
See also Understanding Medical Terminology.