UAS sequences are fused upstream of 3 copies of Tag:HA followed by a genomic fragment that encompasses exons 3 to 5 (including the variable exon 4 cluster) of Dscam1. Dscam1 intron 4.6 has been replaced with Dscam1 intron 9.29. A short 3'UTR from the ewg gene is present downstream of the genomic fragment.