In this work, we have studied four closely related members of the five known Drosophila hnRNP A/B family, hrp36, hrp38, hrp40, and hrp48. Using splicing-sensitive microarrays, between 200 and 300 genes were detected as specifically regulated by each individual hrp protein following down regulation of the protein expression level by RNAi-mediated knock-down. Keywords: Genetic modification Overall design: Each individual protein (four total) were individually knock-down. RNA from biological triplicates were isolated 4 days after the initial treatment. A non-specific RNAi control was performed and the RNA isolated from multiple replicates were pooled and used as control sample in the microarray.