Fig. 3. Identification of intronic sequences of tilapia Ostf1. (A) Possible exon-exon junctions were determined through an analysis of synteny between Tetraodron nigroviridis, Fugu rubripes and Danio rerio genomic sequences based on homology to full-length tilapia Ostf1 mRNA (GenBank AY679524). Blast hits link regions of high similarity between Ostf1 mRNA and the three genomic sequences identified using BLAST. Gray boxes along the genomic representations indicate transcripts predicted using the Ensembl bioinformatics tool. Tilapia exon-exon junctions, predicted from the conserved gene structure of Ostf1 paralogs, are indicated by black arrows over tilapia Ostf1 mRNA. Lengths of predicted introns 1/2 and 2/3 are indicated in base pairs for each genomic representation. (B) Detail of exon 2-exon 3 junction region in tilapia Ostf1 mRNA. The arrow indicates the predicted junction site. PCR primers designed to amplify intron 2/3 are shown. Bold letters in the primer sequences correspond to conserved 3' acceptor and 5' donor consensus sites. (C) Genomic sequence of tilapia Ostf1 intron 2/3 (lowercase), flanked by exons (uppercase). Arrows indicate the position of PCR primers used for amplification. Numbers indicate the sequence position in Ostf1 mRNA and relative intron length (between parentheses).