Some genetic interrelations of methionine mutants of Neurospora crassa

[摘要] Methionine mutants of \(Neurospora crassa\) were isolated by a filtration concentration technique following ultra-violet irradiation. These and other mutants were classified by the physiological tests of precursor utilisation and heterocaryon complementation. Precursor utilisation data are in agreement with the present outline of methionine synthesis from cysteine but provide little information on the pathway of sulphate reduction and incorporation of sulphur within a carbon skeleton to yield cysteine. Seven cysteine and eight methionine loci are represented on the basis of heterocaryon complementation tests. Four of the cysteine loci and either one or two of the methionine loci, associated with the methylation of homocysteine, have not been reported previously. Two of the eight methionine loci had already been located but five of the remainder were associated with definite chromosome regions. No evidence for the tight clustering of either these or the cysteine loci was obtained. Inter-allelic complementation has been observed at two loci and the fine structure of one of these loci (me-2) has been studied in some detail by analysis of prototroph formation in inter-allelic crosses. The use of "outside markers" has facilitated the demonstration of intra-genic recombination and "conversion". Furthermore, these studies provide evidence for a linear arrangement of mutable sites within the locus with additive prototroph frequencies to yield a site map which can be correlated with a complementation map. The results also show that some alleles are more prone to "conversion" than others.

[发布机构] University:University of Birmingham;Department:Department of Microbiology

[关键词] Q Science;QP Physiology