 the carcinogenic and mutagenic effects of the aromatic amines are believed to depend on their covalent modification of dna , primarily through the formation of adducts at c8 of guanine . 
 the actual biologic and biochemical responses to these adducts can be envisioned as the consequence of the abilities of the cell to repair the lesions , with or without fidelity , and the introduction of errors through bypass of the adducts by polymerases . 
 a key question is whether changes in dna sequence arise through the participation of common repair processes that cause mutations independent of adduct structure . 
 alternatively , do mutations arise through miscoding during polymerase bypass at the site of the adducts and are , therefore , more likely to produce sequence changes that are more characteristic of adduct structure ? 
 this question has been approached using single , site - specific , or randomly introduced aromatic amine dna adducts in bacterial cells , and in vitro studies with dna polymerases that employ site - specifically modified templates . 
 the results of both approaches demonstrate that these adducts are distinguished readily by virtue of their structures , thus supporting the conclusion that mutagenic effects of the aromatic amines arise from their structures rather than from their triggering a common inaccurate repair response.imagesfigure 1 . 
Images