Examination of exon 7 to exon 8 splicing in wild type versus TWisallele-specific transcripts. RT-PCR analysis of T +/+, TWis/+, and TWis/TWise7.5 embryo RNA. Genotypes of embryos are indicated above the lanes; + cont = T +/+ RNA control; - cont = no RNA negative control. A. Primer pairs used to amplify the product are indicated to the right (see also Table 1). F1-BGH037, an exon 6-ETn element primer pair, only amplifies from TWis/+ and TWis/TWissamples. F3-R1, a 3' end of exon 7 to exon 8 primer pair, only amplifies from +/+ and TWis/+ samples. B. Additional RT-PCR using primers F3-R1. Size, in base pairs (bp), indicated to the right. * = unincorporated primers visible on the gel. Brackets indicate bands excised, purified, and sequenced. Products were named based on RT-PCR primer set followed by lower case letter next to the bracket (see Table 2).