Mobitec's mammalian expression systems include vectors for Exontrap cloning. The Exontrap vector pET01 has an intrinsic splicing function that enables selective cloning of exon sequences from large genomic eukaryotic DNA fragments. This new route for the identification of eukaryotic genes does not involve an initial isolation of cellular mRNA, allowing genes that are not transcribed during certain life cycle stages to be identified. This greatly facilitates exon/intron mapping.