Genomic organisation of Cylicocyclus nassatus beta tubulin isotype 1. (a) Schematic of published gene  showing order and size of exons and introns. (b) Schematic of proposed gene, showing alternative organisation of exons and introns and position of primers used to amplify three overlapping fragments used to generate contiguous sequence. Exons and introns are represented by boxes and lines, respectively and number of the first amino acid residue of each exon is shown in italics. The position of codons 167 and 200 are marked red and blue boxes, respectively. Schematics are not to scale. (c) PCR using primers 4f and 6r, spanning exons 4 and 5, from genomic DNA template showing co-amplification of two alternative amplicons from four species of cyathostomin. Lanes: 1, Quantitative ladder 4 (Yorkshire Bio, UK), 2 and 3 Cylicocylus nassatus, 4 and 5 Cyathostomum catinatum, 6 and 7 Cylicostephanus longibursatus, 8 and 9 Cylicostephanus goldi. Two products were amplified for each parasite at ~300 bp and ~1800 bp.