DETECTION OF ABERRANT 4:4 ASCI IN ASCOBOLUS IMMERSUS

1978 ◽  
Vol 20 (1) ◽  
pp. 9-17 ◽  
Author(s):  
N. Paquette
Keyword(s):  
Gene Conversion ◽  
High Frequencies ◽  
Ascobolus Immersus ◽  
Very High Frequencies ◽  
Very High ◽  
Hybrid Dna

Ascopore and mycelium markers were used to detect the aberrant 4:4 asci of the mutation b2A4 of the b2 locus of Ascobolus immersus. Previous studies have shown that this mutation produces gene conversion events with many postmeiotic (30+:5 m and 5+:3 m) in addition to meiotic (2+:6 m and 6+:2 m) segregations. But the aberrant 4:4 asci could not be scored because the octads of this fungus are unordered. The asci were screened using round-spored and granular-spored mutants and confirmed with two mycelium markers, a brown mutant and a wave mutant. Very high frequencies of aberrant 4:4 asci were observed in each cross performed (more than 40% of the postmeiotic segregations). This suggested that both chromatids are very often implicated in the process of hybrid DNA formation at this site of the locus.

An ammeter for very high frequencies

1930 ◽  
Vol 68 (401) ◽  
pp. 556-559
Author(s):  
C.L. Fortescue ◽  
L.A. Moxon
Keyword(s):  
High Frequencies ◽  
Very High Frequencies ◽  
Very High

scholarly journals Idiotypic analysis of potential and available repertoires in the arsonate system.

1984 ◽  
Vol 160 (1) ◽  
pp. 1-11 ◽  
Author(s):  
M Slaoui ◽  
O Leo ◽  
J Marvel ◽  
M Moser ◽  
J Hiernaux ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
B Cells ◽  
Keyhole Limpet Hemocyanin ◽  
High Frequencies ◽  
Specific Subset ◽  
A Minor ◽  
Very High Frequencies ◽  
Very High ◽  
Limiting Dilution

We have shown that, by suitable idiotypic manipulation, BALB/c mice can express the major cross-reactive idiotype (CRI) of A/J mice in response to azophenylarsonate (Ars). In order to know if the CRIA idiotype is present in the potential repertoire of BALB/c before any intentional selection, we used polyclonal activation in vitro and limiting dilution analysis. The readout was done with two monoclonal anti-CRIA antibodies that recognize distinct idiotopes on a CRIA+ A/J germline-encoded monoclonal antibody. We studied the frequency of CRIA+ lipopolysaccharide (LPS)-reactive cells in the spleens of nonimmune and immune A/J mice and in the spleens of naive and manipulated (i.e., producing CRIA+ antibodies) BALB/c mice. A/J and BALB/c naive individuals presented very high frequencies of Ars-specific B cells while the frequency of CRIA+ B cells was only a minor subset (0.5%) of the total Ars-specific subset in the two strains. When A/J mice were immunized with Ars-keyhole limpet hemocyanin, a clear preferential expansion of the CRIA+ minor subset of A/J mice was observed (100x). No such enhancement was observed in BALB/c mice similarly treated. Manipulated BALB/c mice presented a higher frequency of CRIA+ anti-Ars B cells than naive or antigen-immunized BALB/c individuals.

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.

A Genetically Marked I Element in Drosophila melanogaster Can Be Mobilized When ORF2 Is Provided in trans

Genetics ◽  
1998 ◽  
Vol 148 (1) ◽  
pp. 267-275
Author(s):  
Isabelle Busseau ◽  
Sophie Malinsky ◽  
Maria Balakireva ◽  
Marie-Christine Chaboissier ◽  
Danielle Teninges ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Heat Shock ◽  
Reverse Transcriptase ◽  
Germ Line ◽  
Ltr Retrotransposons ◽  
Low Frequencies ◽  
High Frequencies ◽  
In Trans ◽  
Very High Frequencies ◽  
Very High

Abstract I factors in Drosophila melanogaster are non-LTR retrotransposons similar to mammalian LINEs. They transpose at very high frequencies in the germ line of SF females resulting from crosses between reactive females, devoid of active I factors, and inducer males, containing active I factors. The vermilion marked IviP2 element was designed to allow easy phenotypical screening for retrotransposition events. It is deleted in ORF2 and therefore cannot produce reverse transcriptase. IviP2 can be mobilized at very low frequencies by actively transposing I factors in the germ line of SF females. This paper shows that IviP2 can be mobilized more efficiently in the germ line of strongly reactive females in the absence of active I factors, when it is trans-complemented by the product of ORF2 synthesized from the hsp70 heat-shock promoter. This represents a promising step toward the use of marked I elements to study retrotransposition and as tools for mutagenesis.

scholarly journals Field Measurements of Dielectric Absorption in Antarctic Ice and Snow at Very High Frequencies

1968 ◽  
Vol 7 (49) ◽  
pp. 89-94 ◽  
Author(s):  
M. E. R. Walford
Keyword(s):  
Impurity Content ◽  
Field Measurements ◽  
Relaxation Mechanism ◽  
Absorption Bands ◽  
High Frequencies ◽  
Dielectric Absorption ◽  
Antarctic Snow ◽  
Radio Frequencies ◽  
Very High Frequencies ◽  
Very High

AbstractField measurements are presented of dielectric absorption in Antarctic snow and ice at frequencies of a few hundred megahertz. They are compared with measurements by other authors at very high frequencies. The dielectric absorption in ice at these frequencies is accounted for in terms of absorption bands both at radio frequencies and in the infrared. Bands at radio frequencies are caused by a relaxation mechanism which depends upon the temperature and the impurity content of the ice. These two factors are therefore included in an account of the dielectric absorption in ice at very high frequencies.

scholarly journals Ephemeral states in protein folding under force captured with a magnetic tweezers design

2019 ◽  
Vol 116 (16) ◽  
pp. 7873-7878 ◽  
Author(s):  
Rafael Tapia-Rojo ◽  
Edward C. Eckels ◽  
Julio M. Fernández
Keyword(s):  
Magnetic Field ◽  
Molten Globule ◽  
Magnetic Tweezers ◽  
Protein L ◽  
High Frequencies ◽  
Electric Signals ◽  
Very High Frequencies ◽  
The Magnetic Field ◽  
Very High ◽  
Unique Capability

Magnetic tape heads are ubiquitously used to read and record on magnetic tapes in technologies as diverse as old VHS tapes, modern hard-drive disks, or magnetic bands on credit cards. Their design highlights the ability to convert electric signals into fluctuations of the magnetic field at very high frequencies, which is essential for the high-density storage demanded nowadays. Here, we twist this conventional use of tape heads to implement one in a magnetic tweezers design, which offers the unique capability of changing the force with a bandwidth of ∼10 kHz. We calibrate our instrument by developing an analytical expression that predicts the magnetic force acting on a superparamagnetic bead based on the Karlqvist approximation of the magnetic field created by a tape head. This theory is validated by measuring the force dependence of protein L unfolding/folding step sizes and the folding properties of the R3 talin domain. We demonstrate the potential of our instrument by carrying out millisecond-long quenches to capture the formation of the ephemeral molten globule state in protein L, which has never been observed before. Our instrument provides the capability of interrogating individual molecules under fast-changing forces with a control and resolution below a fraction of a piconewton, opening a range of force spectroscopy protocols to study protein dynamics under force.

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