Development of Mutagen-Sensitive Strains of Neurospora to Detect Specific Locus Mutations

The host-mediated assay (1) was developed originally to provide an assay for the induction of point mutations in animals treated with potentially mutagenic compounds. Since there is no simple assay that can be made on cells that are a normal component of the animal for point mutations, these investigators introduced an organism in which such an assay could be made. Salmonella was introduced into the peritoneum of the host, incubated for about three hours and then withdrawn for genetic analysis. By using a histidine-requiring strain (G-46) (2), chemicals capable of producing base-pair substitutions could be shown to be genetically active. Additional strains have since been developed by Ames (3) which detect a wider range of genetic alterations, and the most recent tester set (4) is an even more sensitive detector of genetic activity than the original strains. The enhanced sensitivity of the new strains is due in part to the incorporation of a repair-deficient mutation, which results in the conversion of a higher frequency of the genetic damage produced by mutagenic treatment into observed mutation. All of this development has, in effect, made available potent tools for the detection of specific