The distal region of the D. melanogaster Dscam1 exon 6 cluster (extending from a point in the intron downstream of exon 6.35 through to a point in the intron downstream of exon 6.48) has been replaced with the corresponding sequence from D. virilis (extending from a point in the intron downstream of exon 6.41 to a point in the intron downstream of exon 6.52).