Figure 3. Teleost fish IRBP gene loci

A: Zebrafish has two IRBP genes. B: Tetraodon nigroviridis has a remnant of the upstream gene (Gene 1) and a full copy of Gene 2. C: Fugu has two IRBP genes. Panel D: Medaka has a single gene corresponding to Gene 2. In zebrafish and fugu, the two IRBP genes are oriented head to tail, and, across species, the intergenic spacer is about the same size. No intervening genes are found between the two genes in the single locus. The colors originate with the web site computer program called AUGUSTUS [46]. Each exon is marked with two different colors, such that the end of one exon and the beginning of the next exon have the same color. Colors are rotated so that adjacent exons are colored differently (only three colors are needed) and the order of use is blue-red-green, which is then repeated. The first exon of a gene is depicted with an arrow tail at the 5' end, and the last exon is labeled with an arrowhead at the 3' end. For genes that have only a single exon, they are solid blue, with an arrow head and tail. These models are predicted gene structures based on several algorithms. Also, some of the features are small, so that a tiny first exon might not appear to have an arrow tail at the 5' end.