EFFICIENT SELECTION OF 3'-TERMINAL EXONS FROM VERTEBRATE DNA

Identification of expressed sequences within genomic DNA is a hurdle i n the characterization of complex genomes. We developed an exon trappi ng scheme that provides a positive selection for vertebrate 3'-termina l exons. A copy of the trapped exon sequence is obtained by RT/PCR amp lification. The technique detects valid terminal exons without interfe rence from partial exons or non-specific sequences, including simple h uman repeated sequences. Application to random human cosmids yielded o ne unique trapped terminal exon per cosmid on average. Because vertebr ate terminal exons average 600 - 700 nucleotides in length, the techni que provides transcribed sequences of sufficient length to assist furt her mapping efforts.