Abstract
Four different U2-snRNA genes/related sequences of D. melanogaster were cloned and characterized. The sequences of all four genes suggest that they were generated by a DNA-mediated mechanism. These genes/related sequences were found to be located in two loci, each locus containing two U2 snRNA sequences. Using coding sequences as well as flanking sequences as hybridization probes against polytene chromosomes of D. melanogaster Oregon R we were able to map these loci separately at positions 34BC and 84C. By Northern analysis we observed that the quantities of U2- and U1-snRNA are coordinated and change during the embryonic development of the fly.