MUTAGENIC SPECIFICITIES AND ADDUCT DISTRIBUTIONS FOR 7-BROMOMETHYLBENZ[A]ANTHRACENES

Mutation induction in the supF gene of the plasmid pS189 by 7-bromomet hylbenz[a]anthracene and 7-bromomethyl-12-methylbenz[a]anthracene was examined. The former compound was substantially more mutagenic than th e latter but a much greater proportion of the total mutations were loc ated at mutation hotspots for the 12-methyl derivative. The overall co rrelation between sites of mutation and sites of polymerase arrest (an indicator of adduct formation) through the supF gene was poor. Althou gh these bromo-compounds should form only a single guanine adduct (unl ike dihydrodiol epoxides that form both cis and trans adducts) more th an one mutational change was found at a given site, although the predo minant base substitution was G-->T for either compound.