Increasing the Multiplicity of Ribosomal RNA Genes in Drosophila melanogaster

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Science  22 Jan 1971:
Vol. 171, Issue 3968, pp. 294-297
DOI: 10.1126/science.171.3968.294


In wild-type Drosophila melanogaster females there are about 250 ribosomal RNA genes in each nucleolus organizer region of the two X chromosomes. When this same nucleolus organizer region is present in flies in only a single dose, the number of ribosomal RNA genes increases to approximately 400. This increase is most easily explained by disproportionate replication of these genes.