UAS regulatory sequences drive expression of a chimeric protein which consists of the D. melanogaster kay α isoform in which the N-terminal exon has been replaced with the corresponding sequence from the D. pseudoobscura Dpse\kay α isoform. The mRNA produced is sufficiently divergent in sequence from the D. melanogaster kay α isoform to be resistant to the dsRNA produced by the P{NIG.15507R} RNAi construct which targets the N-terminal exon.