ON ARRANGEMENT OF GENES FOR 28S AND 18S RIBOSOMAL RNAS IN DROSOPHILA MELANOGASTER

It is known that 130 or more genes for both 28 s and 18 s ribosomal RNA are present in the haploid nucleus of wild-type Drosophila melanogaster. Furthermore, the two kinds of genes are different and are clustered in a distinct locus (bobbed+). The data reported here indicate that the numerical ratio between genes for 28 s and 18 s rRNA is one, both in the wild-type and in a series of independently obtained partial deletions of the bobbed locus. The elution profile of rRNA-DNA hybrids from nitrocellulose columns was also studied, using both entire ribosomal RNA and purified 28 s rRNA. It is concluded that at least a large fraction of genes for 28 s rRNA are adjacent to genes for 18 s rRNA. © 1968.