Repeated Gene Families in Drosophila melanogaster

This paper is about repeated gene families in Drosophila melanogaster. A repeated gene family consists of many identical or nearly identical genes that cohabit a single haploid genome. In some cases the genes are contained within tandemly repeated DNA units. Indeed, the successive observations that the 18S and 28S rRNA genes in Xenopus laevis (Brown and Weber 1968; Birnstiel et al. 1968; Miller and Beatty 1969), the 5S RNA genes of this frog (Brown et al. 1971), and the histone genes of sea urchins (reviewed by Kedes 1976) are all tandemly repeated created an illusion that repeated gene families generally assume such tandem topographies. It is true that these three repeated genes have been found in tandem arrays in other eukaryotes - notably in D. melanogaster, which is the only species in which each has been isolated and studied in molecular detail. (rRNA genes: Glover and Hogness 1977; White and...