title: The nature and origin of a class of essential gene substitutions in bacteriophage lambda.
mesh_terms: D002874:Chromosome Mapping; D003090:Coliphages / Q000032:analysis / Q000254:growth & development; D004269:DNA, Bacterial / Q000032:analysis; D004279:DNA, Viral / Q000032:analysis; D004926:Escherichia coli / Q000032:analysis; D005796:Genes; D009154:Mutation; D009690:Nucleic Acid Conformation
chemical_list: D004269:DNA, Bacterial; D004279:DNA, Viral