PCR primer sequences from a typical dbSTS record and their relationship to a query sequence that might be searched by e-PCR. (a) A few selected fields are shown from dbSTS record 16273 (GenBank accession no. G09892), including various names and identifiers, the sequences of the forward and reverse primers (both in 5′ → 3′ orientation), the size of the PCR product, and the sequence of the amplicon and flanking regions. (b) For a query sequence that is the same sense as the sequence of the dbSTS record, a successful match will include the forward primer followed by the inverse (i.e., reverse-compliment) of the reverse primer. On the other hand, if the query sequence is of the opposite sense (imagine the lower strand reversed), it will be the reverse primer followed by the inverse of the forward primer.
