The estimation of conversion parameters and the control of conversion in Ascobolus immersus

1978 ◽  
Vol 159 (1) ◽  
pp. 63-73 ◽  
Author(s):  
M. R. T. Wickramaratne ◽  
B. C. Lamb
Keyword(s):  
Ascobolus Immersus

scholarly journals Extensive, Nonrandom Diversity of Excision Footprints Generated by Ds-Like Transposon Ascot-1Suggests New Parallels with V(D)J Recombination

1998 ◽  
Vol 18 (7) ◽  
pp. 4337-4346 ◽  
Author(s):  
Vincent Colot ◽  
Vicki Haedens ◽  
Jean-Luc Rossignol
Keyword(s):  
Extensive Study ◽  
Empty Site ◽  
Site Factors ◽  
Original Sequence ◽  
Ascobolus Immersus ◽  
High Degree ◽  
Hairpin Formation ◽  
Processing Steps ◽  
Color Gene

ABSTRACT Upon insertion, transposable elements can disrupt or alter gene function in various ways. Transposons moving through a cut-and-paste mechanism are in addition often mutagenic when excising because repair of the empty site seldom restores the original sequence. The characterization of numerous excision events in many eukaryotes indicates that transposon excision from a given site can generate a high degree of DNA sequence and phenotypic variation. Whether such variation is generated randomly remains largely to be determined. To this end, we have exploited a well-characterized system of genetic instability in the fungus Ascobolus immersus to perform an extensive study of excision events. We show that this system, which produces many phenotypically and genetically distinct derivatives, results from the excision of a novel Ds-like transposon,Ascot-1, from the spore color gene b2. A unique set of 48 molecularly distinct excision products were readily identified from a representative sample of excision derivatives. Products varied in their frequency of occurrence over 4 orders of magnitude, yet most showed small palindromic nucleotide additions. Based on these and other observations, compelling evidence was obtained for intermediate hairpin formation during the excision reaction and for strong biases in the subsequent processing steps at the empty site. Factors likely to be involved in these biases suggest new parallels between the excision reaction performed by transposons of thehAT family and V(D)J recombination. An evaluation of the contribution of small palindromic nucleotide additions produced by transposon excision to the spectrum of spontaneous mutations is also presented.

scholarly journals Recombination within the Y locus in Ascobolus immersus

1967 ◽  
Vol 9 (2) ◽  
pp. 159-177 ◽  
Author(s):  
A. Kruszewska ◽  
W. Gajewski
Keyword(s):  
Opposite Direction ◽  
Negative Correlation ◽  
Linear Order ◽  
Great Majority ◽  
Wild Type Allele ◽  
Wild Type ◽  
Marker Effect ◽  
Dna Models ◽  
Ascobolus Immersus ◽  
Hybrid Dna

Mutants of the Y locus differed appreciably in their basic conversion frequencies (frequencies of conversion in one-point crosses) to wild type. The differences in the basic conversion frequencies in the opposite direction, i.e. from corresponding wild-type allele to mutant, were in general not pronounced. For some alleles frequencies of conversion in both directions were similar, but for the others they differed markedly. No evident correlation between the position of mutants on the map and their basic conversion frequencies was observed.In two-point crosses in repulsion, the great majority of recombinant octads were of conversion type. In these crosses symmetry or asymmetry of conversion depended mainly on similarity or differences in basic conversion frequencies of mutants crossed. In crosses between mutants from different clusters the recombination frequencies were near to the sums of their basic conversion frequencies. Such ‘mutant specificity’ makes it impossible to establish the linear order of mutants on the basis of recombination frequencies in two-point crosses.The results of two-point crosses in repulsion between mutants within clusters pointed to the influence of one allele on the frequency of conversion of another one. This ‘marker effect’ was also evident in some three-point crosses.The frequencies of simultaneous conversions in two-point crosses in coupling did not show negative correlation with the distances between the mutants involved.It seems that many of the data presented here are most easily explained by recently developed hybrid DNA models.

Nonrandom transition from asymmetrical to symmetrical hybrid DNA during meiotic recombination

Genome ◽  
1989 ◽  
Vol 32 (3) ◽  
pp. 414-419 ◽  
Author(s):  
Angelos Kalogeropoulos ◽  
Jean-Luc Rossignol
Keyword(s):  
Meiotic Recombination ◽  
Heteroduplex Dna ◽  
Dna Distribution ◽  
Left Part ◽  
Ascobolus Immersus ◽  
Two Phases ◽  
The Right ◽  
Hybrid Dna

During meiotic recombination, in the b2 gene of Ascobolus immersus hybrid DNA can be formed either on only one (asymmetrical hybrid DNA) or on both (symmetrical hybrid DNA) interacting chromatids. The two phases can be found in the same meiosis, involving the same two interacting chromatids with the symmetrical phase located on the right with regard to the asymmetrical one. We show that the transition from the asymmetrical to the symmetrical phase occurs in a defined region located within the left part of the gene, which is closer to the initiation region. Once formed, the symmetrical hybrid DNA phase seems always to extend to the rightmost mutation sites. This contrasts with asymmetrical hybrid DNA extension, which when it stays in asymmetrical form, may stop within the gene.Key words: Ascobolus immersus, heteroduplex DNA distribution.

scholarly journals Reciprocal exchanges instigated by large heterologies in the b2 gene of ascobolus are not associated with long adjacent hybrid DNA stretches.

Genetics ◽  
1988 ◽  
Vol 119 (2) ◽  
pp. 329-336
Author(s):  
T Langin ◽  
H Hamza ◽  
V Haedens ◽  
J L Rossignol
Keyword(s):  
Gene Conversion ◽  
Dna Sequence ◽  
Sequence Homology ◽  
Holliday Junctions ◽  
Holliday Junction ◽  
Mendelian Segregation ◽  
Ascobolus Immersus ◽  
Postmeiotic Segregation ◽  
Single Branch ◽  
Hybrid Dna

Abstract In the gene b2 of Ascobolus immersus, large heterologies increase the frequencies of reciprocal exchanges on their upstream border (corresponding to the high non-Mendelian segregation side). Tests were made to determine whether these reciprocal exchanges, instigated by large heterologies, resulted from the blockage of a Holliday junction bordering a hybrid DNA tract extending from the end of the gene to the heterology. Three types of experiments were performed to answer this question. In all cases, results did not correlate the presence of reciprocal exchanges instigated by large heterologies with the presence of adjacent hybrid DNA tracts. These reciprocal exchanges were rarely associated with postmeiotic segregation at upstream markers, they were not associated with gene conversion of a marker within the interval and their frequency was not decreased by decreasing the frequency of hybrid DNA formation in the gene. These results led to the proposal of the existence of a precursor to reciprocal exchange different from a single branch-migrating Holliday junction. This precursor migrates rightward and its migration is dependent on the DNA sequence homology. The existence of this precursor does not exclude that reciprocal exchanges resulting from the maturation of single Holliday junctions bordering adjacent hybrid DNA tracts could also occur.

Proteins are attached to the ends of a linear plasmid in the filamentous fungus Ascobolus immersus

1986 ◽  
Vol 11 (3) ◽  
pp. 243-246 ◽  
Author(s):  
F. Meinhardt ◽  
F. Kempken ◽  
K. Esser
Keyword(s):  
Filamentous Fungus ◽  
Linear Plasmid ◽  
Ascobolus Immersus

New equations and a method for finding nine parameter values for two alleles at one locus to study gene conversion using Ascobolus immersus

Genome ◽  
1992 ◽  
Vol 35 (3) ◽  
pp. 421-427 ◽  
Author(s):  
B. C. Lamb ◽  
S. A. Zwolinski
Keyword(s):  
Gene Conversion ◽  
Control Factors ◽  
Dna Models ◽  
Ascobolus Immersus ◽  
Asymmetric Hybrid ◽  
Quantitative Analyses ◽  
Allele Segregation ◽  
Parameter Values ◽  
Quantitative Treatment ◽  
Hybrid Dna

A quantitative treatment is given for meiotic gene conversion with its parameters and equations for their interactions to determine allele segregation class frequencies from heterozygotes. The possible pairing of both pairs of nonsister chromatids in a bivalent at exactly the same point is included. Using sets of data from Ascobolus immersus, it is shown that values for all nine parameters for hybrid DNA models of recombination can be obtained using an iterative computer program. The accuracy of the values is estimated and the double-strand gap repair model is considered. The parameter values obtained invalidate most of the simplifications used in previous quantitative analyses of gene conversion data. They showed total bias in strand preference in asymmetric hybrid DNA formation and some bias in which type of chromatid is the invading one. There were slight differences in repair frequency between the two types of mispair and very large differences in the direction of repair. Conversion control factors had major effects on hybrid DNA formation and repair of mispairs.Key words: Ascobolus, gene conversion, quantitative analysis, recombination mechanisms.

Molecular cloning and characterization of the met2 gene from Ascobolus immersus

Gene ◽  
1988 ◽  
Vol 63 (2) ◽  
pp. 297-308 ◽  
Author(s):  
Christophe Goyon ◽  
Godeleine Faugeron ◽  
Jean-Luc Rossignol
Keyword(s):  
Molecular Cloning ◽  
Ascobolus Immersus

A COMPARATIVE STUDY OF THE PRODUCTION OF RNA BYROUND SPOREMUTATIONS INASCOBOLUS IMMERSUS

1974 ◽  
Vol 16 (1) ◽  
pp. 39-48 ◽  
Author(s):  
C. Hamelin ◽  
G. H. Cousineau
Keyword(s):  
Comparative Study ◽  
Rna Synthesis ◽  
Wildtype Strain ◽  
Mutant Strains ◽  
Ascobolus Immersus ◽  
Morphological Aberration ◽  
Independent Locus ◽  
Complex Locus ◽  
Independent Series

Ninety-nine spontaneous round spore mutants from Ascobolus immersus were grouped into two independent series designated 828 and 1034. Series 828 is a complex locus with various alleles. Total RNA characterization of three mutants from series 828 and one from series 1034 was done. Significant quantitative differences in RNA content were found between the mutant strains and the wildtype strain S2. In the case of the particular mutant strains, it seems that the expression on RNA synthesis by heteroallelic strains is identical; while it varies for an independent locus it is still responsible for the same morphological aberration in ascospore size.

Sign in / Sign up

Export Citation Format

Share Document