Glycidyl methacrylate （GMA）is a recently recognized mutagen. In order to explore the mutagenicity and mechanism of GMA

plasmid PBR322 was used for in vitro binding

mutant screening

restriction enzyme mapping

and DNA sequencing. To explore the mechamism by which an initial premutational event is converted into a stable heritable mutation

pBR322 and GMA-bound pBR322 were transformed into E. coli HB101

and the following results were obtained : 1) GMA-bound PBR322 induced phenotype changes in competent cells. Two stable and heritable mutants were isolated （Ap￣RTc￣S and Ap￣STc￣R）. 2) When restriction enzyme mapping was used to analyze the mutant Ap￣RTc￣S

four of seven maps showed changes

but no large DNA insertion or deletion were observed.3) The frequency of deletion and insertion forms counted about 10%. Sequence specificity and hot spot regions were evident in the sequence analysis of mutated plasmid. The above results indicate that the premutagenic lesions of plasmid induced by GMA can be converted into point mutations in vivo.