Institute For Allgemeine Mikrobiologie

Bern, Switzerland

Institute For Allgemeine Mikrobiologie

Bern, Switzerland
SEARCH FILTERS
Time filter
Source Type

PubMed | Institute For Allgemeine Mikrobiologie
Type: Journal Article | Journal: Current genetics | Year: 2013

65 trp1(-) alleles of Schizosaccharomyces pombe have been analysed for their interallelic complementation pattern, suppressibility by nonsense suppressors and position of the corresponding mutation site on an intragenic map of the trp1 locus. In addition to the three complementation classes previously described (Schweingruher and Dietrich 1973) as defective in phosphoribosylanthranilate isomerase (trp1A), indole glycerolphosphate synthetase (trp1B) and anthranilate synthetase (trp1C), two new complementation classes, trp1BC and trp1ABC, were found. The former is represented by a single allele which can only complement trp1A mutants. The latter is represented by six alleles which fail to complement tester mutants of the trp1A, trp1B or trp1C class. Classes trp1A, trp1B and trp1C correspond to mutations in three nonoverlapping regions mapping in the order trp1A, trp1B and trp1C All the alleles of the trp1BC and trp1ABC classes correspond to mutations in the trp1C region. Nonsense alleles of the opal (UGA) or ochre (UAA) type were found in the trp1A (2 alleles out of 17) and trp1ABC (5 alleles out of 6) classes only. These data indicate that the trp1 locus is transcribed as a single messenger RNA with transcription starting from the trp1C region. This messenger is probably translated in a single, multifunctional polypeptide, or at most in two polypeptides coded for by the trp1B-trp1C and by the trp1A regions. In addition, the polar effect of nonsense mutations in the trp1C region is cancelled by rare spontaneous mutations occuring at or very near the trp1 locus, which may act by creating an internal single for the initiation of transcription and/or translation.


PubMed | Institute For Allgemeine Mikrobiologie
Type: Journal Article | Journal: Current genetics | Year: 2013

Spontaneous meiotic and mitotic rates of recombination were measured for 50 intragenic intervals in 9 genes of Schizosaccharomyces pombe. A much smaller mitotic/meiotic recombination ratio is observed for genes unlinked to the centromere (average ratio: 0.005) than for genes close to the centromere (up to 0.17). The high ratio observed for the latter genes is due to a high rate of mitotic recombination rather than to a centromeric inhibition of meiotic recombination, since there was no meiotic inhibition in the genes considered. As already reported for one pair of genes in Saccharomyces cerevisiae (Hnaut et Luzzati, 1972), cells that have recombined at one locus have a meiotic rate of coincident recombination at an unlinked locus, even if the latter is not on the same chromosome. This coincidence is much lower when intragenic recombinants are selected in the centromere-linked gene lys1. In modification of an earlier hypothesis (Hurst and Fogel, 1964), we propose that: (a) pairing between homologous chromosomes is the major rate-limiting factor in mitotic recombination; (b) mitotic pairing of homologous chromosomes is frequent, possibly occuring in all vegetative cells, but is usually restricted to the centromere region; and (c) pairing along the whole genome is restricted to a small subpopulation among the mitotically dividing cells.


PubMed | Institute For Allgemeine Mikrobiologie
Type: Journal Article | Journal: Current genetics | Year: 2013

Gene conversion and postmeiotic segregation patterns have been analysed at 14 mutant sites of sup3, sup8 and sup9 including 5 alleles with a strong marker effect on recombination frequencies in two-factor crosses. The total frequency of gene conversion and postmeiotic segregation tetrads is fairly constant within each gene, but may vary from one gene to another. About 97% of the conversion events are coconversions spanning the whole sup gene. Postmeiotic segregations are usually quite rare. None of the marker-effect alleles has an increased rate of hybrid DNA formation at the allele considered, as judged from the frequency of gene conversion and postmeiotic segregation in one-factor crosses. At least two of them, sup3-e and sup9-e, are associated with a high frequency of postmeiotic segregation indicating a poor repair of the corresponding base-pair mismatches. This is also observed in a two-factor cross and can account for the marker effect on recombination frequencies. The properties of a third marker effect allele, sup3-e,r10, are best explained by a higher probability of single site conversions as opposed to coconversions in two-factor crosses involving the mutant site r10.

Loading Institute For Allgemeine Mikrobiologie collaborators
Loading Institute For Allgemeine Mikrobiologie collaborators