A STUDY OF MEIOSIS IN A HAPLOID OF TRITICUM VULGARE VILL. AND ITS PROGENIES

1952 ◽  
Vol 30 (1) ◽  
pp. 40-49 ◽  
Author(s):  
R. C. McGinnis ◽  
John Unrau
Keyword(s):  
High Frequency ◽  
First Generation ◽  
Random Distribution ◽  
Crossing Over ◽  
Third Generation ◽  
Reciprocal Translocations ◽  
Homologous Chromosomes ◽  
Triticum Vulgare ◽  
Normal Pollen

Meiosis was studied in the haploid of Triticum vulgare and in its second and third generation selfed progenies derived from pollination of the haploid with normal pollen. In the haploid, 57.6% of the metaphase cells showed one to three bivalents. This is assumed to be evidence of a degree of homology between chromosomes of the haploid set. Random distribution of univalents to the poles was apparently restricted by bivalent and secondary associations. Cells with 42 chromosomes were observed in a few instances. In one case the complement was made up of 21 bivalents. A high frequency of trivalents and quadrivalents was observed in the second and third generations. Presumably crossing over between partially homologous chromosomes, occurring in the haploid, resulted in reciprocal translocations which were transmitted to succeeding generations. Plants with chromosomal deficiency or duplication, observed in the second and third generations, probably originated from union of unbalanced gametes in first generation plants heterozygous for translocations or deficient or duplicated for one or more chromosomes.

Grandparents Reveal Their Secrets: A New Holocaust Narrative for the Young ‘Third Generation’ in Israel

2012 ◽  
Vol 5 (1) ◽  
pp. 97-110 ◽  
Author(s):  
Yael Darr
Keyword(s):  
Young Children ◽  
First Generation ◽  
Third Generation ◽  
Master Narrative ◽  
Safe Distance ◽  
Domestic Sphere ◽  
Holocaust Memory ◽  
Very Young Children ◽  
The Holocaust ◽  
New Type

Since the 1990s, a new type of Holocaust story has been emerging in Israeli children's literature. This new narrative is directed towards very young children, from preschool to the first years of elementary school, and its official goal is to instil in them an authentic ‘first Holocaust memory’. This essay presents the literary characteristics of this new Holocaust narrative for children and its master narrative. It brings into light a new profile of both writers and readers. The writers were young children during the Holocaust, and first chose to tell their stories from the safe distance of three generations. The readers are their grand-children and their grand-children's peers, who are assigned an essential role as listeners. These generational roles – the roles of a First Generation of writers and of a Third Generation of readers – are intrinsically familial ones. As such, they mark a significant change in the profile of yet another important figure in the Israeli intergenerational Holocaust discourse, the agent of the Holocaust story for children. Due to the new literary initiatives, the task of providing young children with a ‘first Holocaust memory’ is transferred from the educational authority, where it used to reside, to the domestic sphere.

Effect of the Pairing Gene Ph1 and Premeiotic Colchicine Treatment on Intra- and Interchromosome Pairing of Isochromosomes in Common Wheat

Genetics ◽  
1998 ◽  
Vol 150 (3) ◽  
pp. 1199-1208 ◽  
Author(s):  
Juan M Vega ◽  
Moshe Feldman
Keyword(s):  
Common Wheat ◽  
Homologous Chromosome ◽  
Colchicine Treatment ◽  
Crossing Over ◽  
Meiotic Pairing ◽  
Factors Affecting ◽  
Homologous Chromosomes ◽  
Polyploid Wheat ◽  
Main Gene ◽  
Ph1 Gene

Abstract The analysis of the pattern of isochromosome pairing allows one to distinguish factors affecting presynaptic alignment of homologous chromosomes from those affecting synapsis and crossing-over. Because the two homologous arms in an isochromosome are invariably associated by a common centromere, the suppression of pairing between these arms (intrachromosome pairing) would indicate that synaptic or postsynaptic events were impaired. In contrast, the suppression of pairing between an isochromosome and its homologous chromosome (interchromosome pairing), without affecting intrachromosome pairing, would suggest that homologous presynaptic alignment was impaired. We used such an isochromosome system to determine which of the processes associated with chromosome pairing was affected by the Ph1 gene of common wheat—the main gene that restricts pairing to homologues. Ph1 reduced the frequency of interchromosome pairing without affecting intrachromosome pairing. In contrast, intrachromosome pairing was strongly reduced in the absence of the synaptic gene Syn-B1. Premeiotic colchicine treatment, which drastically decreased pairing of conventional chromosomes, reduced interchromosome but not intrachromosome pairing. The results support the hypothesis that premeiotic alignment is a necessary stage for the regularity of meiotic pairing and that Ph1 relaxes this alignment. We suggest that Ph1 acts on premeiotic alignment of homologues and homeologues as a means of ensuring diploid-like meiotic behavior in polyploid wheat.

scholarly journals MITOTIC CROSSING OVER AND NONDISJUNCTION IN TRANSLOCATION HETEROZYGOTES OF ASPERGILLUS

Genetics ◽  
1976 ◽  
Vol 82 (4) ◽  
pp. 605-627
Author(s):  
Etta Käfer
Keyword(s):  
Selective Advantage ◽  
The Other ◽  
Translocation Chromosome ◽  
Crossing Over ◽  
Selective Marker ◽  
Reciprocal Translocations ◽  
Poor Growth ◽  
Different Types ◽  
Diploid Genotype ◽  
One Step

ABSTRACT To analyze mitotic recombination in translocation heterozygotes of A. nidulans two sets of well-marked diploids were constructed, homo- or heterozygous for the reciprocal translocations T1(IL;VIIR) or T2(IL;VIIIR) and heterozygous for selective markers on IL. It was found that from all translocation heterozygotes some of the expected mitotic crossover types could be selected. Such crossovers are monosomic for one translocated segment and trisomic for the other and recovery depends on the relative viabilities of these unbalanced types. The obtained segregants show characteristically reduced growth rates and conidiation dependent on sizes and types of mono- and trisomic segments, and all spontaneously produce normal diploid sectors. Such secondary diploid types either arose in one step of compensating crossing over in the other involved arm, or—more conspicuously—in two steps of nondisjunction via a trisomic intermediate.—In both of the analyzed translocations the segments translocated to IL were extremely long, while those translocated from IL were relatively short. The break in I for T1(I;VII) was located distal to the main selective marker in IL, while that of T2(I;VIII) had been mapped proximal but closely linked to it. Therefore, as expected, the selected primary crossover from the two diploids with T2(I;VIII) in coupling or in repulsion to the selective marker, showed the same chromosomal imbalance and poor growth. These could however be distinguished visually because they spontaneously produced different trisomic intermediates in the next step, in accordance with the different arrangement of the aneuploid segments. On the other hand, from diploids heterozygous for T1(I;VII) mitotic crossovers could only be selected when the selective markers were in coupling with the translocation; these crossovers were relatively well-growing and produced frequent secondary segregants of the expected trisomic, 2n+VII, type. For both translocations it was impossible to recover the reciprocal crossover types (which would be trisomic for the distal segments of I and monosomic for most of groups VII or VIII) presumably because these were too inviable to form conidia.—In addition to the selected segregants of expected types a variety of unexpected ones were isolated. The conditions of selection used favour visual detection of aneuploid types, even if these produce only a few conidial heads and are not at a selective advantage. For T2(I;VIII) these "non-selected" unbalanced segregants were mainly "reciprocal" crossovers of the same phenotype and imbalance as the selected ones. For T1(I;VII) two quite different types were obtained, both possibly originating with loss of the small VII-Itranslocation chromosome. One was isolated when the selective marker in repulsion to T1(I;VII) was used and, without being homo- or hemizygous for the selective marker, it produced stable sectors homozygous for this marker. The other was obtained from both coupling and repulsion diploids and showed a near-diploid genotype; it produced practically only haploid stable sectors of the type expected from monosomics, 2n-1 for the short translocation chromosome.

The Brown Mite, Bryobia arborea Morgan and Anderson (Acarina: Tetranychidae), on Apple in Nova Scotia.: I. Influence of Intratree Distribution on the Selection of Sampling Units. II. Differences in Habits and Seasonal Trends in Orchards With Bivoltine and Trivoltine Populations. III. Distribution of Diapause Eggs. IV. Hatching of Diapause Eggs

1965 ◽  
Vol 97 (12) ◽  
pp. 1303-1318 ◽  
Author(s):  
H. J. Herbert
Keyword(s):  
Nova Scotia ◽  
First Generation ◽  
Second Generation ◽  
Central Area ◽  
Third Generation ◽  
Apple Trees ◽  
Seasonal Trends ◽  
Sample Unit ◽  
The Third ◽  
Selection Of

AbstractIn Nova Scotia one leaf cluster with an adjoining 1 inch of twig taken from the inside of each of 10 apple trees replicated four times is an adequate sample unit to measure the density of the brown mite.The brown mite has one generation with a partial second in some orchards and one with a partial second and partial third in others. The first generation adults in the bivoltine and trivoltine populations lay summer eggs on the leaves and twigs, and diapause eggs on tin twigs. The second generation adults in the bivoltine populations lay only diapause eggs; in the trivoltine populations they lay both summer and diapause eggs. The adults of the third generation lay only diapause eggs.The brown mite is found on both the leaves and woody parts of the tree. In orchards with bivoltine populations the proportion of mites on leaves reached a peak of 80% by mid-July, but thereafter gradually decreased to 10% by the end of August. However, in orchards with trivoltine populations the proportion of mites on leaves reached a peak of 80 to 90% by mid-July, remained constant until mid-August, and thereafter decreased to approximately 40% by the end of August.The number of diapause eggs laid by adults of each generation in both the bivoltine and trivoltine populations varies widely. The eggs are deposited on the trunk as well as on the branches, with the heaviest deposition in the central area of the tree. The diapause eggs laid by adults of the first generation are the last to hatch and those laid by the third generation are the first to hatch the following spring.The factors responsible for the differences in the number of generations and in the number of diapause eggs laid are unknown.

MEIOSIS IN THE GRASSHOPPER. II. THE PRELEPTOTENE SPIRAL STAGE DURING OOGENESIS AND SPERMATOGENESIS IN MELANOPLUS FEMUR-RUBRUM

1972 ◽  
Vol 14 (2) ◽  
pp. 397-401 ◽  
Author(s):  
Kathleen Church
Keyword(s):  
Dna Synthesis ◽  
Crossing Over ◽  
Chromosome Behaviour ◽  
Homologous Chromosomes ◽  
Diploid Complement

Chromosome behaviour occurring from premeiotic DNA synthesis to leptotene of meiosis is described for both males (spermatogenesis) and females (oogenesis) in the grasshopper Melanoplus femur-rubrum. These events include a period of chromosome spiralization and contraction following premeiotic DNA synthesis and prior to leptotene. The diploid complement of chromosomes becomes visible in both sexes. No pairing between homologous chromosomes or chiasmata are observed in either sex. The results suggest that synapsis and crossing over must occur following preleptotene spiralization during spermatogenesis and oogenesis in this grasshopper.

scholarly journals Novel Experimental Study of Fabric Drying Using Direct-Contact Ultrasonic Vibration

2018 ◽  
Vol 11 (2) ◽  
Author(s):  
Viral K. Patel ◽  
Frederick Kyle Reed ◽  
Roger Kisner ◽  
Chang Peng ◽  
Saeed Moghaddam ◽  
...  
Keyword(s):  
High Frequency ◽  
Direct Contact ◽  
First Generation ◽  
Scale Up ◽  
Enthalpy Of Vaporization ◽  
Piezoelectric Transducers ◽  
Scaling Analysis ◽  
Moisture Removal ◽  
Low Efficiency

Abstract Fabric drying is an energy-intensive process, which generally involves blowing hot dry air across tumbling wet fabric to facilitate evaporation and moisture removal. Most of the energy supplied is used to overcome the enthalpy of vaporization for water. Although this process tends to be inefficient, it is fairly simple and forms the basis for the majority of existing clothes dryer technology today. To address the relatively low efficiency, a new method of drying called “direct contact ultrasonic fabric drying” is proposed. The process involves using high-frequency vibration introduced by piezoelectric transducers, which are in contact with wet fabric. The vibration is used to extract water droplets from the fabric mechanically. In this study, a total of 24 individual transducers are used in a module to dry a 142 cm2 sized fabric. The performance characterization of this single module has enabled successful scale-up of the system to a midscale prototype dryer, which can be used to ultrasonically dry clothing-sized fabric (∼750 cm2). The first-generation ultrasonic fabric dryer fabricated uses as little as 17% of the energy needed by traditional evaporation-based drying techniques. In addition to experimental data, this paper presents the results of a kinetic and scaling analysis that provides some important insights into ultrasonic drying.

Human Right to Environment and Its Effective Protection in Catalonia, Spain and Europe

2014 ◽  
Vol 42 (1) ◽  
pp. 121-134
Author(s):  
Alexandre Peñalver i Cabré
Keyword(s):  
Human Rights ◽  
First Generation ◽  
18Th Century ◽  
Third Generation ◽  
Political Rights ◽  
Human Right ◽  
Effective Protection ◽  
Cultural Rights ◽  
Additional Layer ◽  
Civil And Political Rights

Human Right to Environment is one the most relevant Third Generation Human Rights which includes new universal needs arisen from the last third of 20th century. These new human rights add as an additional layer to the First Generation Human Rights (civil and political rights from the end of 18th century) and to the Second Generation Human Rights (economic, social and cultural rights from 19th century).

scholarly journals The Arabidopsis HOP2 Gene Has a Role in Preventing illegitimate Exchanges between Nonhomologous Chromosomes

2021 ◽  
Author(s):  
YIsell Farahani-Tafreshi ◽  
Chun Wei ◽  
Peilu Gan ◽  
Jenya Daradur ◽  
C. Daniel Riggs ◽  
...  
Keyword(s):  
Active Role ◽  
Crossing Over ◽  
Wild Type ◽  
Positive Role ◽  
Homologous Chromosomes ◽  
Chromosome Synapsis ◽  
Radiation Induced ◽  
Nonhomologous Chromosome ◽  
Chromosome Exchanges

Meiotic homologous chromosomes pair up and undergo crossing over. In many eukaryotes both intimate pairing and crossing over require the induction of double stranded breaks (DSBs) and subsequent repair via Homologous Recombination (HR). In these organisms, two key proteins are the recombinases RAD51 and DMC1. Recombinase-modulators HOP2 and MND1 have been identified as proteins that assist RAD51 and DMC1 and are needed to promote stabilized pairing. We have probed the nature of the genetic lesions seen in hop2 mutants and looked at the role of HOP2 in the fidelity of genetic exchanges. Using γH2AX as a marker for unrepaired DSBs we found that hop2-1 and mnd1 mutants have different appearance/disappearance for DSBs than wild type, but all DSBs are repaired by mid-late pachytene. Therefore, the bridges and fragments seen from metaphase I onward are due to mis-repaired DSBs, not unrepaired ones. Studying Arabidopsis haploid meiocytes we found that wild type haploids produced the expected five univalents, but hop2-1 haploids suffered many illegitimate exchanges that were stable enough to produce bridged chromosomes during segregation. Our results suggest that HOP2 has a significant active role in preventing nonhomologous associations. We also found evidence that HOP2 plays a role in preventing illegitimate exchanges during repair of radiation-induced DSBs in rapidly dividing petal cells. Thus, HOP2 plays both a positive role in promoting homologous chromosome synapsis and a separable role in preventing nonhomologous chromosome exchanges. Possible mechanisms for this second important role are discussed.

scholarly journals Philosophy from the outside in: Rosenzweig’s critical project

2012 ◽  
Vol 23 (2) ◽  
pp. 65-76
Author(s):  
Willi Goetschel
Keyword(s):  
First Generation ◽  
Martin Buber ◽  
Third Generation ◽  
Literary Modernism ◽  
The Third ◽  
Jewish Thought ◽  
Two Generations ◽  
The University ◽  
Critical Intervention ◽  
Hermann Cohen

This paper examines Rosenzweig?s philosophic project in the context of his time as a critical intervention in the discussion of the place of Jewish thought in the university and in society. If Hermann Cohen represented the first generation of Jewish philosophers claiming that participation in the university is constitutive for the institution?s claim to universalism, the second generation-represented by Martin Buber - was more diffident about the university and its openness. For Buber, literary modernism offered what the university would refuse. Disappointed about the failure of the recognition of the efforts of the previous two generations, Rosenzweig represents the third generation. He turns the situation into a creative response anchoring philosophy as a project that calls for a resolute move outside the university.

scholarly journals Therapeutic Drug Monitoring of Second- and Third-Generation Antiepileptic Drugs: Insights From a College of American Pathologists Proficiency Testing Survey

2021 ◽  
Author(s):  
Matthew D. Krasowski ◽  
Thomas A. Long ◽  
Christine L. H. Snozek ◽  
Annabel Dizon ◽  
Barbarajean Magnani ◽  
...  
Keyword(s):  
Therapeutic Drug Monitoring ◽  
Antiepileptic Drugs ◽  
Proficiency Testing ◽  
Drug Monitoring ◽  
First Generation ◽  
Therapeutic Drug ◽  
Third Generation ◽  
Enzyme Immunoassays ◽  
Steady Growth ◽  
Survey Results

Context.— Therapeutic drug monitoring has traditionally been widely used for first-generation antiepileptic drugs (AEDs) such as carbamazepine and phenytoin. The last 2 decades have seen the introduction of second- and third-generation AEDs (eg, lamotrigine, levetiracetam, and topiramate) into clinical practice. Objective.— To use data from the College of American Pathologists Therapeutic Drug Monitoring, Extended proficiency testing survey to determine the performance of assays used for therapeutic drug monitoring of newer AEDs, including comparison of enzyme immunoassay and chromatographic techniques. Design.— Six years of proficiency testing surveys were reviewed (2013–2018). Results.— Steady growth was seen in participant volumes for newer AEDs. The analytical performance of automated enzyme immunoassays for lamotrigine, levetiracetam, and topiramate was similar to that of chromatographic methods, consistent with published literature using patient samples for comparisons. The majority of participating laboratories now use enzyme immunoassays to measure levetiracetam. Conclusions.— Survey results reflect steadily growing interest in therapeutic drug monitoring of newer AEDs. The increasing availability of robust immunoassays for new AEDs should facilitate their clinical utility, especially for clinical laboratories that do not perform chromatographic assays for therapeutic drug monitoring.

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