This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ong, T.-m. Articles by de Serres, F. J. Search for Related Content PubMed PubMed Citation Articles by Ong, T.-m. Articles by de Serres, F. J.

Genetic Characterization of Adenine-3 Mutants Induced by 4-Nitroquinoline 1-Oxide and 4-Hydroxyaminoquinoline 1-Oxide in Neurospora crassa¹

Environmental Mutagenesis Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709

Specific locus mutations induced by the chemical carcinogens, 4-nitroquinoline 1-oxide (4NQO) and 4-hydroxyaminoquinoline 1-oxide (4HAQO), have been characterized to obtain a presumptive identification of the genetic alterations at the molecular level. One hundred eighty-four 4NQO-induced and 219 4HAQO-induced ad-3 mutants of Neurospora crassa obtained in previous studies were studied with a series of genetic tests that permits determination of their genotype and the frequencies of point mutations and multilocus deletions. These tests have shown that the spectrum of ad-3 mutations among 4NQO-induced mutants is similar to that of 4HAQO-induced mutants. None of the 4NQO- or 4HAQO-induced mutants is a multilocus deletion mutant. The ratio of ad-3A to ad-3B mutants is the same in the two samples, as well as the frequencies of complementing ad-3B mutants. These data suggest, then, that the mechanism of mutation induction by 4NQO in N. crassa is identical to that of 4HAQO. It is not clear, however, whether 4NQO is mutagenic per se or reduction of 4NQO to 4HAQO is the first step involved in the mutagenesis of this compound in Neurospora.

The heterokaryon tests have shown that the relatively high frequencies of 4NQO- or 4HAQO-induced ad-3B mutants show allelic complementation and that most of the complementing ad-3B mutants (74% of 4NQO induced and 71% of 4HAQO induced) have nonpolarized complementation patterns. From this we conclude that both agents induce predominantly base-pair substitution mutations in N. crassa. The results are in agreement with our other studies which show that potent chemical carcinogens induce predominantly base-pair substitution mutations in N. crassa.

¹ Research jointly sponsored by National Institute of Environmental Health Sciences and the United States Atomic Energy Commission under contract with the Union Carbide Corporation.

² Present address: Biological and Medical Research Division, Sandoz Ltd., Basle, Switzerland.

Received 3/14/74. Accepted 10/10/74.