An uvsB mutant of Aspergillus nidulans with high variable spontaneous mutation and intergenic mitotic recombination frequencies.

An UV-sensitive mutant has been isolated with a new technique which allows isolation of UV-sensitive and UV-non-mutable mutants in Aspergillus nidulans. This mutant is an allele of the known uvsB gene but shows some features not previously described in the alleles so far isolated. Its more important characteristics are: (1) Frequency of mitotic intergenic recombination is strongly increased in uvs/uvs diploids and it is highly variable in different clones: it varies from a minimum of 40-fold to a maximum of about 1000-fold in comparison with uvs+/uvs+ strains. (2) The frequency of mitotic intergenic recombination is increased also in the heterozygous diploids. (3) The frequency of spontaneous mutation is higher and highly variable in different subclones: it may be increased up to 1000-fold.