Figure 1.

Mutually exclusively spliced tandem exon duplication-derived substitution in the Dscam1 gene. (A) A selection of Drosophila gene Dscam1 transcript models from the UCSC genome browser (21). Dscam1 has four separate sets of homologous exons - each transcript includes just one of the four sets of exons. Regions with the homologous exons are indicated by the arrows. (B) The ten crystalised structures from the PDB (22) of the first four immunoglobulin domains in Dscam1 protein (18) shown in cartoon format. The constant regions in the ten proteins are shown in different colours, while the homologous regions translated from the two 5′ tandem exon duplication-derived substitutions are shown in red. All 10 structures are highly similar despite the differences in sequence, but loop regions translated from the homologous exons have distinct backbones. The structures in all figures were represented using PyMol.