The induction of temperature-sensitive mutations in Drosophila melanogaster by the acridine mustard ICR-170

Mutagenicity of some intercalating agents in Chinese hamster V79 cells

ICR 170 and ICR 191, but not 9-aminoacridine or chloroquine, induced both 6-thioguanine- and, to a smaller extent, ouabain-resistance in Chinese hamster V79 cells. These results indicate that covalent binding to DNA is necessary for intercalating agents to induce mutation in this cell line, and that this assay can distinguish potential carcinogens from non-carcinogenic analogues of this chemical type. The induction of ouabain-resistance by both ICR 170 and ICR 191 indicates that these frameshift mutagens induce base-pair substitution to some extent in V79 cells.

Chemical carcinogens transform BHK cells by inducing a recessive mutation

Treatment of BHK cells with mutagenic carcinogens induced neoplastic transformation in a single step. This transformation displayed the characteristics expected for a recessive mutation. Increasing doses of carcinogens induced transformants with kinetics similar to the kinetics with which they induced 6-thioguanine-resistant or ouabain-resistant mutants in the same population of cells. Transformants with temperature-restricted phenotypes were easily induced by carcinogens which cause mutations by base changes, but when ICR frameshift mutagens were used, the proportion of temperature-limited transformants was inversely related to the frequency with which a particular mutagen induced frameshift mutations. In hybrids between pseudodiploid isogenic strains of normal and transformed BHK cells, transformation was expressed as a dominant trait when the transformed parent was induced by a papovavirus, but was suppressed as a recessive trait when the transformed parent arose spontaneously or was chemically induced. Segregation of transformation was observed upon growth of suppressed normal hybrids, and the transformed phenotype which was reexpressed was in most cases characteristics of the original transformed parent.

Chemical carcinogens transform BHK cells by inducing a recessive mutation

Treatment of BHK cells with mutagenic carcinogens induced neoplastic transformation in a single step. This transformation displayed the characteristics expected for a recessive mutation. Increasing doses of carcinogens induced transformants with kinetics similar to the kinetics with which they induced 6-thioguanine-resistant or ouabain-resistant mutants in the same population of cells. Transformants with temperature-restricted phenotypes were easily induced by carcinogens which cause mutations by base changes, but when ICR frameshift mutagens were used, the proportion of temperature-limited transformants was inversely related to the frequency with which a particular mutagen induced frameshift mutations. In hybrids between pseudodiploid isogenic strains of normal and transformed BHK cells, transformation was expressed as a dominant trait when the transformed parent was induced by a papovavirus, but was suppressed as a recessive trait when the transformed parent arose spontaneously or was chemically induced. Segregation of transformation was observed upon growth of suppressed normal hybrids, and the transformed phenotype which was reexpressed was in most cases characteristics of the original transformed parent.

Isolation and characterization of deficiencies exposing the rudimentary locus of Drosophila melanogaster

Therudimentarylocus ofDrosophila melanogastercontains the structural information for the first three enzymes of thede novopyrimidine pathway. Two newrudimentary (r)mutants have been isolated following mutagenesis with ICR-170. From complementation analysis and cyto-genetical observation both were shown to be deficiencies which expose therlocus.Df(1)r19is deleted from band 14D1 to 15D1 andDf(1)r1Dfrom band 14B6 to 15A2. These deficiencies were combined with several characterizedralleles each giving a single enzymatic defect in one of the first three enzymes of the pyrimidine pathway. An unusual semilethaltranseffect was observed in some but not all the combinations. The effect was not observed with a third smaller deficiency which also exposes therudimentarylocus.

Mechanism of hycanthone mutagenesis: the induction of temperature-sensitive mutations in Drosophila melanogaster

A total of 358 sex-linked recessive lethals induced by hycanthone methane sulphonate (HMS) were checked for temperature sensitivity, along with 239 EMS-induced lethals as a positive control. Only about 1-2% of the HMS-induced lethals were temperature-sensitive, in contrast to about 7-8% for EMS-induced lethals. This can be reasonably explained by assuming that in Drosophila, HMS mainly acts by inducing frame-shift mutations or deletions.