Conserved sequences among independent ESTs and their position relative to the A. acetabulum carbonic anhydrase ( AaCA1 ) genomic sequence. a: Structure of the AaCA1 genomic sequence. Positions in the intron and 3'UTR where sequence was omitted are indicated by slanted, heavy double lines. The white boxes represent AaCA1 exons, the hatched box represents the 3' UTRs. The black boxes represent three regions of strong homology between different EST sequences and the AaCA1 gene and the AaCA2 mRNA. b, c and d: sequence alignments of the AaCA1 gene and different ESTs (singletons or clusters) over these three conserved regions. The name of the EST or gene from which each sequence originates is indicated in front of the sequence. The regions of the AaCA1 and AaCA2 genes shown in the alignment are indicated in parentheses. * indicates a consensus in at least 70% of the sequences aligned. - indicates a gap in the alignment. The presence of a polyA/T tract at the end of an EST is indicated by "(A/T)" in front of the EST name.