a) Distribution of the intron length (in percentage) within the two sets of introns: The experimental set (48 introns) that was obtained by comparing N. ovalis cDNAs with gDNAs and the predicted set (145 introns) that was obtained by comparison of N. ovalis gDNAs with P. tetraurelia proteins. The predicted set contains three longer introns that are not shown in this histogram (76, 114 and 252 nt long). b) Schematic representation of the exon/intron boundaries with WebLogo in 48 introns. The GTA and TAG motifs are well conserved. c) Conservation of intron location between N. ovalis and P. tetraurelia in two genes that are orthologous to Succinyl-CoA ligase. Introns were considered conserved when they were within 2 amino acids of each other in the protein alignment. Intron I of N. ovalis and II of P. tetraurelia are conserved. Intron II of N. ovalis and I of P. tetraurelia are not conserved. Whether Intron III of P. tetraurelia is conserved or not cannot be determined.