Apparent discontinuous transcription of Trypanosoma brucei variant surface antigen genes

The repeated mini-exon sequence that encodes the first 35 base pairs of all variant surface antigen mRNAs of Trypanosoma brucei directs the synthesis of a discrete 137-nucleotide transcript. It thus seems that variant surface antigen mRNAs are transcribed discontinuously, and we present two alternative models for how this might occur.