HIGH FREQUENCY OF 3:1 TETRAD RATIOS FOR THE PDX-1 LOCUS OF NEUROSPORA CRASSA

1969 ◽  
Vol 11 (1) ◽  
pp. 60-64 ◽  
Author(s):  
A. Radford ◽  
S. F. H. Threlkeld
Keyword(s):  
Neurospora Crassa ◽  
Gene Conversion ◽  
High Frequency ◽  
High Ratio ◽  
The Other ◽  
Linked Gene

Nine crosses, involving three alleles, were used in a study of recombination at the pdx-1 locus of Neurospora. In two of the crosses, an unusually high ratio of apparent gene conversion was observed, Two asci of the aberrant type were analyzed by means of prototrophs from backcrosses. In one case the ascus was confirmed as an example of genuine gene conversion. In the other, however, the original scoring of the ascus was found to be due to the presence of a closely linked gene capable of modifying the expression of the two conditional pdx-1 mutants used in the study.

scholarly journals UNIDIRECTIONAL GENE CONVERSION ASSOCIATED WITH TWO INSERTIONS IN NEUROSPORA CRASSA MITOCHONDRIAL DNA

Genetics ◽  
1979 ◽  
Vol 93 (3) ◽  
pp. 645-654
Author(s):  
Carmen A Mannella ◽  
Alan M Lambowitz
Keyword(s):  
Mitochondrial Dna ◽  
Neurospora Crassa ◽  
Gene Conversion ◽  
High Frequency ◽  
The Other ◽  
Wild Type ◽  
Eco Ri

ABSTRACT The mitochondrial phenotype of [poky] and other extranuclear Neurospora mutants is known to predominate over that of wild type in hetero-plasmons. In the present work, we have investigated the interaction between wild-type and [poky] mtDNAs using as many as four physical markers to distinguish the two types of mtDNAs. Two insertions, one of 1200 bp in Eco RI-5 and the other 50 bp in Eco RI-9, are identified as sites of high frequency, unidirectional gene conversion leading to their spread through mtDNA populations in heteroplasmons. However, the transmission of the [poky] mutation does not appear to be correlated with the transmission of either of these insertions or of other physical markers. The possibility that other loci of nonreciprocal recombination might be responsible for the "dominance" of Neurospora extranuclear mutants is discussed.

Relative clauses in Agul from a corpus-based perspective

2020 ◽  
Vol 73 (1) ◽  
pp. 113-158
Author(s):  
Timur Maisak
Keyword(s):  
High Frequency ◽  
Relative Clauses ◽  
High Ratio ◽  
The Other ◽  
The Core ◽  
Text Corpora ◽  
The Asymmetry ◽  
Intransitive Verbs ◽  
Syntactic Restrictions ◽  
Locative Case

AbstractThis paper gives an account of participial clauses in Agul (Lezgic, Nakh-Daghestanian), based on a sample of 858 headed noun-modifying clauses taken from two text corpora, one spoken and one written. Noun-modifying clauses in Agul do not show syntactic restrictions on what can be relativized, and hence they instantiate the type known as GNMCCs, or general noun-modifying clause constructions. As the text counts show, intransitive verbs are more frequent than transitives and experiencer verbs in participial clauses, and among intransitive verbs, locative statives with the roots ‘be’ and ‘stay, remain’ account for half of all the uses. The asymmetry between the different relativization targets is also significant. Among the core arguments, the intransitive subject (S) is the most frequent target, patient (P) occupies second place, and agent (A) is comparatively rare. The preference of S and, in general, of S and P over A also holds true for most other Nakh-Daghestanian languages for which comparable counts are available. At the same time, Agul stands apart from the other languages by its high ratio of non-core relativization which accounts for 42% of all participial clauses. Addressee, arguments and adjuncts encoded with a locative case, as well as more general place and time relativizations show especially high frequency, outnumbering such arguments as experiencers, recipients, and predicative and adnominal possessors. Possible reasons for the high ratio of non-argument relativization are discussed in the paper.

scholarly journals Chance or Necessity—The Fungi Co−Occurring with Formica polyctena Ants

Insects ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 204
Author(s):  
Igor Siedlecki ◽  
Michał Gorczak ◽  
Alicja Okrasińska ◽  
Marta Wrzosek
Keyword(s):  
Molecular Identification ◽  
High Frequency ◽  
Its Rdna ◽  
The Other ◽  
Formica Polyctena ◽  
Ant Nests ◽  
Mutualistic Fungi ◽  
The Tropics ◽  
High Diversity ◽  
Better Than

Studies on carton nesting ants and domatia−dwelling ants have shown that ant–fungi interactions may be much more common and widespread than previously thought. Until now, studies focused predominantly on parasitic and mutualistic fungi–ant interactions occurring mostly in the tropics, neglecting less−obvious interactions involving the fungi common in ants’ surroundings in temperate climates. In our study, we characterized the mycobiota of the surroundings of Formica polyctena ants by identifying nearly 600 fungal colonies that were isolated externally from the bodies of F. polyctena workers. The ants were collected from mounds found in northern and central Poland. Isolated fungi were assigned to 20 genera via molecular identification (ITS rDNA barcoding). Among these, Penicillium strains were the most frequent, belonging to eight different taxonomic sections. Other common and widespread members of Eurotiales, such as Aspergillus spp., were isolated very rarely. In our study, we managed to characterize the genera of fungi commonly present on F. polyctena workers. Our results suggest that Penicillium, Trichoderma, Mucor, Schwanniomyces and Entomortierella are commonly present in F. polyctena surroundings. Additionally, the high diversity and high frequency of Penicillium colonies isolated from ants in this study suggest that representatives of this genus may be adapted to survive in ant nests environment better than the other fungal groups, or that they are preferentially sustained by the insects in nests.

Normal Synaptonemal Complex and Abnormal Recombination Nodules in Two Alleles of the Drosophila Meiotic Mutant mei-W68

Genetics ◽  
2003 ◽  
Vol 163 (4) ◽  
pp. 1337-1356 ◽  
Author(s):  
Adelaide T C Carpenter
Keyword(s):  
Electron Microscopy ◽  
Synaptonemal Complex ◽  
High Frequency ◽  
Serial Section ◽  
The Other ◽  
Wild Type ◽  
Recombination Nodules ◽  
Section Electron ◽  
Serial Section Electron Microscopy ◽  
Section Electron Microscopy

Abstract The meiotic phenotypes of two mutant alleles of the mei-W68 gene, 1 and L1, were studied by genetics and by serial-section electron microscopy. Despite no or reduced exchange, both mutant alleles have normal synaptonemal complex. However, neither has any early recombination nodules; instead, both exhibit high numbers of very long (up to 2 μm) structures here named “noodles.” These are hypothesized to be formed by the unchecked extension of identical but much shorter structures ephemerally seen in wild type, which may be precursors of early recombination nodules. Although the mei-W68L1 allele is identical to the mei-W681 allele in both the absence of early recombination nodules and a high frequency of noodles (i.e., it is amorphic for the noodle phene), it is hypomorphic in its effects on exchange and late recombination nodules. The differential effects of this allele on early and late recombination nodules are consistent with the hypothesis that Drosophila females have two separate recombination pathways—one for simple gene conversion, the other for exchange.

scholarly journals Gene Conversion Alone Accounts for More Than 90% of Recombination Events at the am Locus of Neurospora crassa

Genetics ◽  
1996 ◽  
Vol 143 (1) ◽  
pp. 129-136 ◽  
Author(s):  
Frederick J Bowring ◽  
David E A Catcheside
Keyword(s):  
Molecular Markers ◽  
Neurospora Crassa ◽  
Gene Conversion ◽  
Holliday Junctions ◽  
Crossing Over ◽  
Gene Markers ◽  
General Significance ◽  
Flanking Sequences ◽  
Simple Conversion

Abstract We have used closely flanking molecular markers located ~4 kb distal and 6 kb proximal of the am locus to investigate the incidence of crossover events associated with the generation of prototrophic recombinants in a cross heteroallelic am1 am6. Ninety-three percent of prototrophs were generated by events that did not recombine the molecular markers, indicating that simple conversion accounts for the formation of most prototrophs and that associated crossovers are much less frequent (~0.07) than estimated previously using more distant flanking markers. This suggests that conversion and crossing over during meiosis may arise from distinct mechanisms or that if, as is widely supposed, conversion and crossing over result from alternate modes of resolution of Holliday junctions then, at least for the am locus of Neurospora, the mode of resolution is strongly biased in favor of retaining the parental association of flanking sequences. Because estimates of the association of conversion and crossing over based on more distant gene markers are similar for yeast and Neurospora (~0.35), our observation may have general significance.

LONG DURATION ECHOES FROM AURORA, METEORS, AND IONOSPHERIC BACK-SCATTER

1953 ◽  
Vol 31 (2) ◽  
pp. 171-181 ◽  
Author(s):  
D. W. R. McKinley ◽  
Peter M. Millman
Keyword(s):  
Long Range ◽  
High Frequency ◽  
The Other ◽  
Very High Frequency ◽  
Long Duration ◽  
E Region ◽  
Very High ◽  
Visual Observations

In the course of the Ottawa meteor program some unusual echoes have been detected on 33 Mc. Echoes from the aurora are discussed and correlated with visual observations. Two mechanisms of radio reflections from the aurora have been proposed but the data here presented are insufficient to favor one over the other. On Aug. 4, 1948, six extremely long duration meteor echoes were observed which may have been due to abnormal ionospheric conditions. From time to time since August, 1948, a weak semipermanent echo has been recorded, usually appearing at a range of about 80 km., and enduring up to an hour. It is suggested that this echo is due to back-scatter from the same sources in the lower E-region that are presumed to be responsible for long-range very high frequency propagation.

scholarly journals Transduction mechanisms of bacteriophage ε15I. General properties of the system

1971 ◽  
Vol 18 (1) ◽  
pp. 9-19 ◽  
Author(s):  
R. W. Hedges
Keyword(s):  
High Frequency ◽  
Genetic Material ◽  
Recipient Strain ◽  
The Other ◽  
Donor Strain ◽  
General Properties ◽  
Show Evidence ◽  
Transduction Mechanisms ◽  
Defective Prophage

SUMMARYBacteriophageεγis capable of transduction both by replacement of a genetic segment of the recipient by the homologous genetic material from the donor strain and by the formation of defective transducing particles capable of lysogenizing the recipient strain ofS. anatum.The isolation of strains carrying such prophages, which have incorporated the lactose or arabinose operons, is reported. Lysogenic strains, carrying both normal and defective transducing prophage, form high-frequency transducing lysates. Other strains, carrying only defective prophage, show evidence that the association of prophage genes and transduced materials is stable since the loss of one frequently entails loss of the other.

High-frequency germ line gene conversion in transgenic mice

1992 ◽  
Vol 12 (6) ◽  
pp. 2545-2552
Author(s):  
J R Murti ◽  
M Bumbulis ◽  
J C Schimenti
Keyword(s):  
Gene Conversion ◽  
Dna Sequences ◽  
High Frequency ◽  
Germ Line ◽  
Gene Families ◽  
Histochemical Staining ◽  
Evolutionary Significance ◽  
Evolutionary Divergence ◽  
Lacz Gene ◽  
Male Gametes

Gene conversion is the nonreciprocal transfer of genetic information between two related genes or DNA sequences. It can influence the evolution of gene families, having the capacity to generate both diversity and homogeneity. The potential evolutionary significance of this process is directly related to its frequency in the germ line. While measurement of meiotic inter- and intrachromosomal gene conversion frequency is routine in fungal systems, it has hitherto been impractical in mammals. We have designed a system for identifying and quantitating germ line gene conversion in mice by analyzing transgenic male gametes for a contrived recombination event. Spermatids which undergo the designed intrachromosomal gene conversion produce functional beta-galactosidase (encoded by the lacZ gene), which is visualized by histochemical staining. We observed a high incidence of lacZ-positive spermatids (approximately 2%), which were produced by a combination of meiotic and mitotic conversion events. These results demonstrate that gene conversion in mice is an active recombinational process leading to nonparental gametic haplotypes. This high frequency of intrachromosomal gene conversion seems incompatible with the evolutionary divergence of newly duplicated genes. Hence, a process may exist to uncouple gene pairs from frequent conversion-mediated homogenization.

Two separate regions of the extrachromosomal ribosomal deoxyribonucleic acid of Tetrahymena thermophila enable autonomous replication of plasmids in Saccharomyces cerevisiae

1981 ◽  
Vol 1 (6) ◽  
pp. 535-543
Author(s):  
G B Kiss ◽  
A A Amin ◽  
R E Pearlman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
High Frequency ◽  
Deoxyribonucleic Acid ◽  
Tetrahymena Thermophila ◽  
The Other ◽  
Yeast Cells ◽  
Origin Of Replication ◽  
Autonomous Replication ◽  
Coding Regions ◽  
Dna Fragment

Plasmids containing the nontranscribed central and terminal, but not the coding, regions of the extrachromosomal ribosomal deoxyribonucleic acid (rDNA) of Tetrahymena thermophila are capable of autonomous replication in Saccharomyces cerevisiae. These plasmids transform S. cerevisiae at high frequency; transformants are unstable in the absence of selection, and plasmids identical to those used for transformation were isolated from the transformed yeast cells. One plasmid contains a 1.85-kilobase Tetrahymena DNA fragment which includes the origin of bidirectional replication of the extrachromosomal rDNA. The other region of Tetrahymena rDNA allowing autonomous replication of plasmids in S. cerevisiae is a 650-base pair, adenine plus thymine-rich segment from the rDNA terminus. Neither of these Tetrahymena fragments shares obvious sequence homology with the origin of replication of the S. cerevisiae 2-microns circle plasmid or with ars1, an S. cerevisiae chromosomal replicator.

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