scholarly journals Increased intragenic recombination and non-disjunction in the Rec-1 strain of Caenorhabditis elegans

1988 ◽  
Vol 51 (2) ◽  
pp. 89-93 ◽  
Author(s):  
B. Rattray ◽  
A. M. Rose
Keyword(s):  
Caenorhabditis Elegans ◽  
Gene Conversion ◽  
Recombination Frequency ◽  
Spontaneous Mutation ◽  
Selective Advantage ◽  
Dna Lesions ◽  
Intragenic Recombination ◽  
Crossing Over ◽  
Spontaneous Mutation Rate ◽  
Independent Events

SummaryThe Rec-1 strain of Caenorhabditis elegans increases recombination frequency three-fold. In this paper, we have investigated the effect of Rec-1 on the intragenic recombination phenomena of crossing-over and gene conversion. These events were increased two- to three-fold as was X-chromosome non-disjunction. All of the recovered recombinants were independent events, indicating that Rec-1 does not act pre-meiotically. The pattern of recombination in the Rec-1 strain resembles a meiotic pattern more than a radiation expansion. We conclude from this result that the Rec-1 enhancement of recombination is not the result of an increased number of DNA lesions randomly distributed along the chromosome. The increased recombination frequency of Rec-1 was not accompanied by any detrimental effects on growth, progeny number or spontaneous mutation rate. In this regard, the results may have implications for models which propose either selective advantage or disadvantage accompanying increased recombination.

scholarly journals Inherited Differences in Crossing Over and Gene Conversion Frequencies Between Wild Strains of Sordaria fimicola From “Evolution Canyon”

Genetics ◽  
2001 ◽  
Vol 159 (4) ◽  
pp. 1573-1593
Author(s):  
Muhammad Saleem ◽  
Bernard C Lamb ◽  
Eviatar Nevo
Keyword(s):  
Genetic Variation ◽  
Gene Conversion ◽  
Spontaneous Mutation ◽  
Crossing Over ◽  
Natural Genetic Variation ◽  
Evolution Canyon ◽  
Wild Strains ◽  
Sordaria Fimicola ◽  
First And Second Generation ◽  
Consistent Direction

Abstract Recombination generates new combinations of existing genetic variation and therefore may be important in adaptation and evolution. We investigated whether there was natural genetic variation for recombination frequencies and whether any such variation was environment related and possibly adaptive. Crossing over and gene conversion frequencies often differed significantly in a consistent direction between wild strains of the fungus Sordaria fimicola isolated from a harsher or a milder microscale environment in “Evolution Canyon,” Israel. First- and second-generation descendants from selfing the original strains from the harsher, more variable, south-facing slope had higher frequencies of crossing over in locus-centromere intervals and of gene conversion than those from the lusher north-facing slopes. There were some significant differences between strains within slopes, but these were less marked than between slopes. Such inherited variation could provide a basis for natural selection for optimum recombination frequencies in each environment. There were no significant differences in meiotic hybrid DNA correction frequencies between strains from the different slopes. The conversion analysis was made using only conversions to wild type, because estimations of conversion to mutant were affected by a high frequency of spontaneous mutation. There was no polarized segregation of chromosomes at meiosis I or of chromatids at meiosis II.

scholarly journals GENETIC ORGANIZATION IN CAENORHABDITIS ELEGANS: FINE-STRUCTURE ANALYSIS OF THE unc-22 GENE

Genetics ◽  
1979 ◽  
Vol 91 (1) ◽  
pp. 95-103 ◽  
Author(s):  
D G Moerman ◽  
D L Baillie
Keyword(s):  
Drosophila Melanogaster ◽  
Fine Structure ◽  
Caenorhabditis Elegans ◽  
Gene Conversion ◽  
Structure Analysis ◽  
Intragenic Recombination ◽  
Preliminary Estimate ◽  
Recessive Mutations ◽  
Fine Structure Analysis ◽  
New Alleles

ABSTRACT Fine-structure analysis of the unc-22 gene of Caenorhabditis elegarns has revealed a number of sites that are separable by recombination. Eight new ethyl methanesulfonate-induced recessive mutations of the unc-22 gene have been isolated. Using these new alleles, as well as e66, a number of separable sites have been identified and positioned relative to one another. The map distances obtained are found to be comparable to those associated with intragenic recombination in Drosophila melanogaster, indicating that genetic finestructure analysis is feasible in Caenorhabditis elegans. Evidence of possible gene conversion is presented. A preliminary estimate of the unc-22 gene size is 2.4 × 10-2 map units.

scholarly journals Mismatch repair systems might facilitate the chromosomal recombination induced by N-nitrosodimethylamine, but not by N-nitrosodiethylamine, in Drosophila

Mutagenesis ◽  
2020 ◽  
Vol 35 (2) ◽  
pp. 197-206
Author(s):  
Tomoe Negishi ◽  
Kenji Yamada ◽  
Keiko Miyamoto ◽  
Emiko Mori ◽  
Kentaro Taira ◽  
...  
Keyword(s):  
Mismatch Repair ◽  
Mutation Rate ◽  
Spontaneous Mutation ◽  
Dna Lesions ◽  
Spot Test ◽  
Dna Double Strand Breaks ◽  
Spontaneous Mutation Rate ◽  
Futile Cycle ◽  
Strand Breaks ◽  
Chromosomal Recombination

Abstract Mismatch repair (MMR) systems play important roles in maintaining the high fidelity of genomic DNA. It is well documented that a lack of MMR increases the mutation rate, including base exchanges and small insertion/deletion loops; however, it is unknown whether MMR deficiency affects the frequency of chromosomal recombination in somatic cells. To investigate the effects of MMR on chromosomal recombination, we used the Drosophila wing-spot test, which efficiently detects chromosomal recombination. We prepared MMR (MutS)-deficient flies (spel1(−/−)) using a fly line generated in this study. The spontaneous mutation rate as measured by the wing-spot test was slightly higher in MutS-deficient flies than in wild-type (spel1(+/−)) flies. Previously, we showed that N-nitrosodimethylamine (NDMA)-induced chromosomal recombination more frequently than N-nitrosodiethylamine (NDEA) in Drosophila. When the wing-spot test was performed using MMR-deficient flies, unexpectedly, the rate of NDMA-induced mutation was significantly lower in spel1(−/−) flies than in spel1(+/−) flies. In contrast, the rate of mutation induced by NDEA was higher in spel1(−/−) flies than in spel1(+/−) flies. These results suggest that in Drosophila, the MutS homologue protein recognises methylated DNA lesions more efficiently than ethylated ones, and that MMR might facilitate mutational chromosomal recombination due to DNA double-strand breaks via the futile cycle induced by MutS recognition of methylated lesions.

scholarly journals Recombination and Spontaneous Mutation at the Major Cluster of Resistance Genes in Lettuce (Lactuca sativa)

Genetics ◽  
2001 ◽  
Vol 157 (2) ◽  
pp. 831-849
Author(s):  
Doris B Chin ◽  
Rosa Arroyo-Garcia ◽  
Oswaldo E Ochoa ◽  
Rick V Kesseli ◽  
Dean O Lavelle ◽  
...  
Keyword(s):  
Gene Conversion ◽  
Resistance Genes ◽  
Spontaneous Mutation ◽  
Large Chromosome ◽  
Crossing Over ◽  
Unequal Crossing Over ◽  
Chimeric Genes ◽  
Recessive Mutations ◽  
Major Cluster ◽  
Genetic Mechanisms

Abstract Two sets of overlapping experiments were conducted to examine recombination and spontaneous mutation events within clusters of resistance genes in lettuce. Multiple generations were screened for recombinants using PCR-based markers flanking Dm3. The Dm3 region is not highly recombinagenic, exhibiting a recombination frequency 18-fold lower than the genome average. Recombinants were identified only rarely within the cluster of Dm3 homologs and no crossovers within genes were detected. Three populations were screened for spontaneous mutations in downy mildew resistance. Sixteen Dm mutants were identified corresponding to spontaneous mutation rates of 10–3 to 10–4 per generation for Dm1, Dm3, and Dm7. All mutants carried single locus, recessive mutations at the corresponding Dm locus. Eleven of the 12 Dm3 mutations were associated with large chromosome deletions. When recombination could be analyzed, deletion events were associated with exchange of flanking markers, consistent with unequal crossing over; however, although the number of Dm3 paralogs was changed, no novel chimeric genes were detected. One mutant was the result of a gene conversion event between Dm3 and a closely related homolog, generating a novel chimeric gene. In two families, spontaneous deletions were correlated with elevated levels of recombination. Therefore, the short-term evolution of the major cluster of resistance genes in lettuce involves several genetic mechanisms including unequal crossing over and gene conversion.

THE SUPPRESSION OF GENE CONVERSION AND INTRAGENIC CROSSING OVER IN ASCOBOLUS IMMERSUS: EVIDENCE FOR MODIFIERS ACTING IN THE HETEROZYGOUS STATE

Genetics ◽  
1974 ◽  
Vol 76 (2) ◽  
pp. 221-243
Author(s):  
J Girard ◽  
J L Rossignol
Keyword(s):  
Genetic Distance ◽  
Gene Conversion ◽  
The Other ◽  
Intragenic Recombination ◽  
Crossing Over ◽  
Heterozygous State ◽  
Heterozygous Condition ◽  
Pigmentation Gene ◽  
Ascobolus Immersus ◽  
Intergenic Recombination

ABSTRACT Four distinct systems cv1, cv2, cv4 and cv6 behaving as monogenic factors have been found in the stock 28 of Ascobolus immersus. They each specifically suppress gene conversion in a spore pigmentation gene (respectively, b1, b2, b4 and b6). In the gene b2, where this phenomenon was studied in most detail, the effect of cv2 on the suppression of gene conversion is almost total; intragenic recombination is very strongly diminished and crossing over is also affected. In the genes b1, b2 and b4 the suppression of conversion is observed only when the corresponding modifier (cv1, cv2 and cv4) is in the heterozygous condition. It is likely that cv6 acts in the same way on b6. cv1 and b1 on one hand, cv2 and b2 on the other, are very closely linked; no recombination was observed between these modifiers and the corresponding spore pigmentation genes. The same genetic distance is observed between the linked genes b4 and b6 and between cv4 and cv6. This could indicate that these two modifiers are also closely linked to the corresponding genes. A possible effect of cv4 on intergenic recombination between b4 and b6 was shown: here again it acts by diminishing the frequency of recombination when cv4 is in the heterozygous state. The problem of the nature of the cv modifiers is discussed.

scholarly journals Structure of the DNA damage-inducible gene DDR48 and evidence for its role in mutagenesis in Saccharomyces cerevisiae.

1990 ◽  
Vol 10 (6) ◽  
pp. 3174-3184 ◽  
Author(s):  
J M Treger ◽  
K McEntee
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Heat Shock ◽  
Spontaneous Mutation ◽  
Dna Lesions ◽  
Open Reading Frames ◽  
Peptide Sequence ◽  
Yeast Cells ◽  
Spontaneous Mutation Rate ◽  
Heat Shock Stress ◽  
Diploid Cells

The DDR48 gene of Saccharomyces cerevisiae is a member of a set of genes that displays increased transcription in response to treatments that produce DNA lesions or to heat-shock stress. Other members of this group include the DDRA2 and UBI4 genes. DNA sequence analysis of the DDR48 gene demonstrates the presence of two overlapping open reading frames, each of which has the capacity to encode a protein with a molecular mass of approximately 45 kilodaltons. Fusions of the DDR48 coding sequences to lacZ demonstrates that only one of these frames is expressed in yeast cells. The protein predicted from this sequence is extremely hydrophilic and contains multiple repeats of the peptide sequence Ser-Asn-Asn-X-Asp-Ser-Tyr-Gly where X is either Asn or Asp. Additionally, closely related sequences are found throughout the primary sequence. Primer extension data indicate that, after 4-nitroquinoline-1-oxide and heat-shock treatments, there are three major and two minor transcriptional start sites which are utilized. The function of the DDR48 gene was investigated by disrupting this gene in diploid cells. Viable haploid cells containing the DDR48 gene disruption were isolated after tetrad analysis. Although the ddr48 mutant showed a slightly altered sensitivity to killing by 4-nitroquinoline-1-oxide and to heat shock compared with the DDR48 haploid, the spontaneous mutation rate of reversion of a his4 mutation was reduced 6- to 14-fold in the ddr48 strain. These results implicate the DDR48 gene in the production or recovery of mutations in S. cerevisiae.

scholarly journals Effects of mutagen-sensitive mus mutations on spontaneous mitotic recombination in Aspergillus.

Genetics ◽  
1992 ◽  
Vol 130 (4) ◽  
pp. 717-728
Author(s):  
P Zhao ◽  
E Kafer
Keyword(s):  
Mitotic Recombination ◽  
Dna Lesions ◽  
Intragenic Recombination ◽  
Chromosome Loss ◽  
Crossing Over ◽  
Induced Mutants ◽  
Radiation Induced ◽  
Mitotic Gene Conversion ◽  
Single Allele ◽  
Repair Genes

Abstract Methyl methane-sulfonate (MMS)-sensitive, radiation-induced mutants of Aspergillus were shown to define nine new DNA repair genes, musK to musS. To test mus mutations for effects on mitotic recombination, intergenic crossing over was assayed between color markers and their centromeres, and intragenic recombination between two distinguishable adE alleles. Of eight mutants analyzed, four showed significant deviations from mus+ controls in both tests. Two mutations, musK and musL, reduced recombination, while musN and musQ caused increases. In contrast, musO diploids produced significantly higher levels only for intragenic recombination. Effects were relatively small, but averages between hypo- and hyperrec mus differed 15-20-fold. In musL diploids, most of the rare color segregants resulted from mitotic malsegregation rather than intergenic crossing over. This indicates that the musL gene product is required for recombination and that DNA lesions lead to chromosome loss when it is deficient. In addition, analysis of the genotypes of intragenic (ad+) recombinants showed that the musL mutation specifically reduced single allele conversion but increased complex conversion types (especially recombinants homozygous for ad+). Similar analysis revealed differences between the effects of two hyperrec mutations; musN apparently caused high levels solely of mitotic crossing over, while musQ increased various conversion types but not reciprocal crossovers. These results suggest that mitotic gene conversion and crossing over, while generally associated, are affected differentially in some of the mus strains of Aspergillus nidulans.

scholarly journals Sex-related differences in crossing over in Caenorhabditis elegans.

Genetics ◽  
1990 ◽  
Vol 126 (2) ◽  
pp. 355-363
Author(s):  
M C Zetka ◽  
A M Rose
Keyword(s):  
Caenorhabditis Elegans ◽  
Maternal Age ◽  
Elevated Temperatures ◽  
Recombination Frequency ◽  
Paternal Age ◽  
Crossing Over ◽  
Nematode Caenorhabditis Elegans ◽  
Male Recombination ◽  
Group I ◽  
The Right

Abstract In the nematode Caenorhabditis elegans, hermaphrodite recombination has been characterized and is the basis of the genetic map used in this organism. In this study we have examined male recombination on linkage group I and have found it to be approximately one-third less than that observed in the hermaphrodite. This decrease was interval-dependent and nonuniform. We observed less recombination in the male in 5 out of 6 intervals examined, and no observable difference in one interval on the right end of LG I. Hermaphrodite recombination frequencies are the result of recombination in two germlines; oocyte and hermaphrodite spermatocytes. We have measured recombination in the oocyte and have found it to be approximately twofold lower than that calculated for hermaphrodite spermatocytes and not significantly different from the male spermatocyte frequency. Thus, recombination frequencies appear to be a function of gonad physiology rather than the sex of the germline. Evidence from experiments examining the effect of karyotype on recombination in males sexually transformed by the her-1 mutation into XO hermaphrodites (normally XX), suggests the sexual phenotype rather than genotype determines the recombination frequency characteristic of a particular sex. Hermaphrodite recombination is known to be affected by temperature, maternal age, and the rec-1 mutation. We have examined the effect of these parameters on recombination in the male and have found male recombination frequency increased with elevated temperatures and in the presence of Rec-1, and decreased with paternal age.

Structure of the DNA damage-inducible gene DDR48 and evidence for its role in mutagenesis in Saccharomyces cerevisiae

1990 ◽  
Vol 10 (6) ◽  
pp. 3174-3184
Author(s):  
J M Treger ◽  
K McEntee
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Heat Shock ◽  
Spontaneous Mutation ◽  
Dna Lesions ◽  
Open Reading Frames ◽  
Peptide Sequence ◽  
Yeast Cells ◽  
Spontaneous Mutation Rate ◽  
Heat Shock Stress ◽  
Diploid Cells

The DDR48 gene of Saccharomyces cerevisiae is a member of a set of genes that displays increased transcription in response to treatments that produce DNA lesions or to heat-shock stress. Other members of this group include the DDRA2 and UBI4 genes. DNA sequence analysis of the DDR48 gene demonstrates the presence of two overlapping open reading frames, each of which has the capacity to encode a protein with a molecular mass of approximately 45 kilodaltons. Fusions of the DDR48 coding sequences to lacZ demonstrates that only one of these frames is expressed in yeast cells. The protein predicted from this sequence is extremely hydrophilic and contains multiple repeats of the peptide sequence Ser-Asn-Asn-X-Asp-Ser-Tyr-Gly where X is either Asn or Asp. Additionally, closely related sequences are found throughout the primary sequence. Primer extension data indicate that, after 4-nitroquinoline-1-oxide and heat-shock treatments, there are three major and two minor transcriptional start sites which are utilized. The function of the DDR48 gene was investigated by disrupting this gene in diploid cells. Viable haploid cells containing the DDR48 gene disruption were isolated after tetrad analysis. Although the ddr48 mutant showed a slightly altered sensitivity to killing by 4-nitroquinoline-1-oxide and to heat shock compared with the DDR48 haploid, the spontaneous mutation rate of reversion of a his4 mutation was reduced 6- to 14-fold in the ddr48 strain. These results implicate the DDR48 gene in the production or recovery of mutations in S. cerevisiae.

Sign in / Sign up

Export Citation Format

Share Document