Transcripts produced from the TWisallele of T. A. Genomic organization of the T gene: introns (black line) not to scale; exons (colored boxes) to scale as per scale bar. In the TWisallele of T, a 5.5 kilobase pair ETn element is inserted immediately 3' of exon 7, as shown by the pink bar (not to scale). (Adapted from [10, 16], and Bernhard G. Herrmann personal communication). Primers used for RT-PCR are indicated (not to scale), where the arrow indicates the approximate primer position within the exon or ETn element. Primer ETn1 used for PCR is located within the ETn insertion approximately 1.3kb 3' of primer BGH037. B. Wild type T transcript: 5' and 3' UTR sequences are in black; ORF sequences in various colors, with exon numbers indicated. RT-PCR products amplified from this RNA in T +/+ embryo controls are indicated to the right (see Table 2). C. Structures of TWisRNA species transcribed from TWisallele as deduced from amplified RT-PCR products (indicated to the right, see Table 2) assuming that transcripts are wild type 5' and 3' of the RT-PCR primers used to amplify products. Note that the RT-PCR product 6,7+ETn could have amplified from any of three transcripts. In no case was wild type T RNA detected in RT-PCR on TWis/TWisembryo RNA.