<正> Objective: To establish a reformative detection system which has sound ability of providing information on molecular mutagenesis spectrum and the specificity of detection system of repackaged λ phage. Methods: LacZ gene

as mutational target gene and reporter gene

was applied into the detection system. The λ gt11 DNA treated with ENU （1-ethyl-1-nitrosourea） and 9-AA （9-aminoacridine） was repackaged in vitro. The packaged λ phage was then grown in E. coli Y1090 on a selective plate containing X-gel and IPTG. The survival and mutation frequencies were determined by counting the clear-plaque and blue-plaque

and the molecular mutation mechanism was studied by extracting and sequencing the LacZ gene of mutants. Results: The survival of repackaged λ phages treated with 9-AA and ENU apparently decreased in consistent dose-dependence. The mutation frequency of clear-plaque mutants showed a linear dose-related increase. The predominant mutations induced by 9-AA were ± 1 frameshift mutation

and 9-AA induc