Protocol describes how to prepare double-stranded RNA (dsRNA) for RNA interference in Drosophila by synthesis of individual RNA strands from linearized plasmid templates, followed by annealing of the strands. DsRNA molecules with a length of 500-800 bp seem to be most active. The dsRNA can be made from cDNA or genomic DNA templates, as long as most of the dsRNA corresponds to presumptive exon sequence.
