Repair-Resistant Mutation in Neurospora

Abstract

Chronic UV treatment produces severalfold fewer mutations in Neurospora conidia than does the same total dose of acute UV. Experiments were designed to determine the conditions required for chronic UV mutagenesis. Measurement of the coincidence frequency for two independent mutations revealed the existence of a subset of cells which are mutable by chronic UV. Analysis of forward mutation at the mtr locus showed that the genetic alterations produced by chronic UV were virtually all point mutants, even though the assay system could detect alterations or deletions extending into neighboring genes. A significant fraction of the mutants produced by acute UV were multigenic deletions. The size of the dose-rate effect (acute UV mutation frequency divided by chronic UV mutation frequency) was compared for several different mutation assay systems. Forward mutations (recessive lethals and mtr) gave values ranging from four to nine. For events which were restricted to specific molecular sites (specific reversions and nonsense suppressor mutations), there was a wider range of dose-rate ratios. This suggests that chronic UV mutation may be restricted to certain molecular sequences or configurations.

Induction of mutation in Neurospora Crassa using neem (Azadirachta Indica A. Juss) leaf extract

“…It enabled intensive use of N. crassa for the artificial induction of mutation and the investigation of the molecular mechanism of mutation (16)(17)(18) . Furthermore, this fungus can make a lot of identical, mostly haploidnucleated conidia, which makes it possible to study spontaneous and natural mutation (19,20) . Artificial mutations can be used to produce auxotrophic mutants.…”