The structure of the Dscam gene in six Drosophila spp. The mature mRNA of each gene contains 22 exons, four of which (exon 4, exon 6, exon 9 and exon 17, shown in green, blue, yellow and red, respectively) are chosen from a cluster of alternative exons. The remaining 18 exons, shown in metallic gray, are always selected. Introns are not shown. Red lines indicate an example choice of exons.
Anastassiou et al. Genome Biology 2006 7:R2 doi:10.1186/gb-2006-7-1-r2