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A gene (bb) in Drosophila melanogaster producing a small bristle phenotype. The locus of bb is very near the centromere, and bb is the only gene known to have alleles on both the X and Y chromosomes. The plus allele of bb is the nucleolus organizer, and the various hypomorphic alleles may represent partial deletions of ribosomal DNA. See Chronology, 1966, Ritossa, Atwood, and Spiegelman.

Subjects: Genetics and Genomics.

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