P elements inserted in the vicinity of or within the Drosophila snRNP SmD3 gene nested in the first intron of the Ornithine Decarboxylase Antizyme gene affect only the expression of SmD3.

The Drosophila gene for snRNP SmD3 (SmD3) is contained in reverse orientation within the first intron of the Ornithine Decarboxylase Antizyme (AZ) gene. Previous studies show that two closely linked P elements cause the gutfeeling phenotype characterized by embryonic lethality and aberrant neuronal and muscle cell differentiation. However, the exact nature of the gene(s) affected in the gutfeeling phenotype remained unknown.