title: Clustered third-base substitutions among wild strains of Escherichia coli.
abstract: Nucleotide sequences of translated regions of the trp operon in 12 wild strains of Escherichia coli reveal striking uniformity among eight strains (suggesting recent common ancestry and supporting the importance of periodic selection in natural populations) and clustered substitutions in four strains (implicating events affecting runs of nucleotides).
mesh_terms: D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial
chemical_list: D004269:DNA, Bacterial