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.