expressed sequence tag

(Abbreviation: EST). Partially sequenced cDNA clone. Because the read length of a standard DNA sequencing reaction is shorter than the majority of cDNA clones, full length sequence can only be obtained by further manipulations. For the purposes of (1) assigning putative function to a cDNA and (2) designing PCR primers to extract the genomic DNA equivalent to the cDNA, full length sequence is usually unnecessary. By restricting sequencing to a single run, large numbers of cDNAs can be characterized at the EST level.