Organisation of the murine B"-encoding genes and their transcripts. The boxes represent the exons (on scale) and the lines represent the introns (not on scale). The coding regions (black boxes) and untranslated regions (white boxes) are indicated. Splicing events are denoted by dotted lines. Below the genomic structures, all putative transcripts are indicated: the main transcripts are coloured in black (at least 5 EST clones were retrieved), while less abundant transcripts are coloured in grey (less than 5 EST clones were found). Primers used for RT-PCR are also indicated (forward primers: B72, B130, Bδ1, Bδ2 and Bδ3/4; reverse primers: E1 to E9).