Another two genes controlling mitotic intragenic recombination and recovery from UV damage in Aspergillus nidulans IV. Genetic analysis of mitotic intragenic recombinants from uvs+/uvs+, uvsD/uvsD and uvsE/uvsE diploids

Abstract

This paper presents the results of a genetic analysis of a number of spontaneous mitotic p-aminobenzoic acid-independent recombinants from uvs+/uvs+, uvsD53/uvsD53 and uvsE82/uvsE82 diploids that are heteroallelic at the pabaA locus. Intragenic recombination in each of the three strains is largely nonreciprocal and may usually result from gene conversion. Gene conversion may be strongly correlated with crossing-over between outside markers in the uvsE82/uvsE82 diploid. Conversion shows no polarity in the uvs+/uvs+diploid; in the uvsE82/uvsE82 diploid there is almost no conversion of the distal pabaA allele; the proximal allele probably converts more often in uvsE82/uvsE82 but this is obscured by the high back-mutation rate of the proximal allele. Whether there is any polarity of gene conversion in the uvsD53/uvsD53 diploid cannot be inferred from the results. More than half of the recombinants from the uvsD53/uvsD53 diploid have an apparently complex origin and may have arisen by double exchanges or by second-order recombination. No such complex recombinants have arisen from the uvsE82/uvsE82 diploid and their frequency among recombinants from the uvs+/uvs+ strain is 16%. The frequency of appearance of these complex recombinants in our strains seems to be correlated with the frequency of intragenic recombination in the particular strains, as influenced by the uvs allele they bear.