scholarly journals Studies on synapsis. II.—Parallel conjugation and the prophase complex in Periplaneta with special reference to the premeiotic telophase

1920 ◽  
Vol 91 (640) ◽  
pp. 305-329 ◽  
Keyword(s):  
Direct Evidence ◽  
Cell Structure ◽  
Alternative Interpretation ◽  
Homologous Chromosomes ◽  
Suitable Material ◽  
Independent Segregation ◽  
The One ◽  
High Degree ◽  
Further Development ◽  
Very High

The reality of synapsis, or the pairing of chromosomes of biparental origin preparatory to their segregation during the maturation divisions of the germ cells, provides at present the most fruitful basis for any attempt to correlate genetic phenomena with cell structure; and it rests upon data derived from sources that are strictly independent of the behaviour of the chromosomes during the remarkable series of events intercalated in the prophase of the heterotype mitosis. It is, however, only possible to gain a knowledge regarding the manner in which homologous chromosomes are brought into association with one another by a study of the meiotic phase itself. To the earlier workers the reality of synapsis was the all-absorbing problem, while the means by which it is effected formed a secondary consideration. It is possible, given the conjugation of chromosomes derived from alternate parents, to explain the independent segregation of allelomorphic pairs on the assumption that their material basis resides in different bivalents; while their localisation in identical bivalents affords an equally satisfactory interpretation of the phenomena of coupling and repulsion. Indeed were coupling and repulsion always absolute the mode of synapsis would not present an urgent cause for enquiry. The progress made of late years, however, in the investigation of partial linkages, makes it imperative for the further development of the chromosome hypothesis to postulate some mechanism for the exchange of chromatin particles between conjugating elements; so that the degree of intimacy involved in the synaptic union assumes a new significance. While recognising with the utmost respect the brilliant speculations of Prof. Morgan and his school, it cannot be truthfully stated that there exists among cytologists at present a very high degree of unanimity as to the line along which the solution of this question must lie. In recent years the belief in telosynapsis (end-to-end union) has increased in prestige among botanical cytologists, while the alternative interpretation of parasynapsis (parallel conjugation) has found greater favour among those who have studied animal forms. In attempting to interpret satisfactorily the events of the meiotic phase in the case of animals, interest centres pre-eminently in those phenomena which intervene between the last premeiotic telophase and the formation of the “bouquet” on the one hand, and the process by which the reduced and longitudinally split (diplotene) segments become transformed into heterotype chromosomes on the other. The former furnish direct evidence of the relation of the meiotic filaments to the somatic chromosomes, while the latter in the light of the subsequent mitotic processes afford indirect data regarding the mode of synapsis, the reality of synapsis being assumed. Regarding the first, to an impartial student the work of the Schreiners (1) 1906, Jannsens (2) 1909, Agar (3) 1911, and Wilson (4) 1912, based in each case on particularly suitable material as regards both size and seriation, cannot fail to carry the conviction that here at least there is a fusion of whole chromosomes parasyndetically; and such an interpretation is fully consonant with the usual derivation of the heterotype chromosomes by separation along the line of cleavage in the diplotene filaments. There are, however, particular cases, notably among Flatworms and Orthoptera, where certain authors (Goldschmidt (5), Sutton(31), Davis (32), and Buchner (6), e. g .) have described the genesis of the tetrads in a manner which can only be reconciled with the theory of synapsis on the assumption that the conjugating elements are united by their extremities alone. In the case of plants the position is somewhat different; here, according to the most recent and very lucid account of Miss Digby for Osmunda, provision is made for the conjugation of univalents in the second contraction, while the fusion witnessed in the first contraction figures involves the reassociation of half chromosomes split in preparation for an arrested division in the preceding telophase. The chief issue between the rival schools in this case concerns not primarily that suggested by the etymological distinction, but the significance of the earlier stages in the meiotic phase. The telosynaptists interpret the first contraction in terms of the premeiotic prophase, whereas the parasynaptic school, like Grégoire (7), attempt to compare it with the bouquet zygotene processes in animals.

scholarly journals A STUDY OF LINKAGE DISEQUILIBRIUM IN BRITISH POPULATIONS OF DROSOPHILA SUBOBSCURA

Genetics ◽  
1979 ◽  
Vol 92 (3) ◽  
pp. 983-994 ◽  
Author(s):  
B Charlesworth ◽  
D Charlesworth ◽  
M Loukas
Keyword(s):  
Linkage Disequilibrium ◽  
Geographical Variation ◽  
Direct Evidence ◽  
Drosophila Subobscura ◽  
Broad Agreement ◽  
Enzyme Loci ◽  
Linkage Disequilibrium Measure ◽  
High Degree ◽  
Individual Enzyme ◽  
Very High

ABSTRACT Data have been obtained concerning the genetic content of samples of O chromosomes from three British populations, and J chromosomes from one population, of Drosophila subobscura. Some improvements to the genetic map of the O and J chromosomes have been made. Allele frequencies at the loci studied do not show much geographical variation, except where associations with geographically varying gene arrangements distort the picture. Striking nonrandom associations between alleles at three enzyme loci and closely linked O chromosome gene arrangements are present. Some historical explanation for these associations cannot at present be ruled out, but it is clear that a very high degree of genetic differentiation must exist between different gene arrangements in this species. There is no convincing direct evidence for linkage disequilibrium between pairs of enzyme loci, although there is a significant association between close linkage and a high value of the linkage disequilibrium measure. This suggests that there may be disequilibria between closely linked enzyme loci that are too small to be individually detectable. These results are in broad agreement with those reported by workers on other Drosophila species. At present there appears to be no evidence to support the concept that selection is sufficiently strong at individual enzyme loci to produce a high degree of nonrandom associations. (FRANKLIN and LEWONTIN 1970).

VIII. On the structure and development of the skull in the ostrich tribe

1866 ◽  
Vol 156 ◽  
pp. 113-183 ◽  
Keyword(s):  
The Other ◽  
The One ◽  
High Degree ◽  
Very High

T he present paper is intended to be the first of a series on the Anatomy of the Vertebrate Skull; and I have chosen the cranium and face of the Ostriches as a startingpoint, principally because of the mid position of these birds in the vertebrate subkingdom, and, in some degree also, because of their generalized character. Indeed, to any one familiar, on the one hand, with the structure of the skull in the higher mammalian types, and on the other with that of the osseous fishes, the skull of an Ostrich is interesting and important in a very high degree; serving, at it does, as a key to open up the meaning of parts so extremely unlike as the true homologues in the Fish and in the Mammal often are. And further, whilst aiding the anatomist in revealing the true morphological counterparts in the highest, as compared with the lowest types, the skull of an ostrich does also form a link of the utmost value for connecting together that of a cold-blooded and that of a warm-blooded creature.

scholarly journals De Traditionele Hofhouding Bij de bin Kanyok van Zaire

Afrika Focus ◽  
1989 ◽  
Vol 5 (1-2) ◽  
pp. 21-63
Author(s):  
Patrick Wymeersch
Keyword(s):  
Political System ◽  
Colonial Period ◽  
The Other ◽  
Political Organization ◽  
The Political ◽  
Royal Family ◽  
Royal Court ◽  
The One ◽  
High Degree ◽  
Very High

The Traditional Royal Court Among the bin Kanyok of Zaire This description represents what was more or less an ideal conception of political organization and kingship before the colonial period. If the traditional systems of ruling still remain, the material symbolism of kingship disappeared mostly in the scene of daily life in the king’s large capital. Looking at the political organization, two seemingly contradictory features emerge. On the one hand, there are the politically quasi-independent lineages living in the villages. The chief or eldest of a lineage is at the same time chief of the whole village. On the other hand, there is the formal political organization, build on a hierarchical model and imposed from the top. This political system is notable for its very high degree of centralization, and especially for the strong authority and power of the divine king. For the purpose of government, the kingdom is divided into sub-districts, containing several villages of an area, districts and provinces. They all depend, in hierarchy,from the capital. The capital accommodates most of the members of the royal family, numerous wives and children from the king and the ministers. The king’s compound, standing in the middle of the capital, is surrounded by a fence. This compound is divided into four specific parts and contains several houses and the palace of the king. On both sides of the royal compound, there is a main street where the ministers and their families live. The king’s person is surrounded by a number of taboos. No one could see him eat in his private kitchen. The principal problem in the political organization is that of the administering the rest of the Kanyok empire, of keeping as a political unit a population divided into autonomous lineages. The model that is followed is, in general, typical of the kingdoms of the southern savanna belt of Zaire. Therefore the structure is pyramidal: the king at the apex delegates his power and authority to the governors. Their position duplicates that of the king, but on a smaller scale. The king is assisted by his ministers to whom he assigned highly specific functions. The king still remains the main focus for all the Bin Kanyok.

scholarly journals Empathy and Dyspathy with Androids: Philosophical, Fictional, and (Neuro)Psychological Perspectives

Konturen ◽  
2010 ◽  
Vol 2 (1) ◽  
pp. 101 ◽  
Author(s):  
Catrin Misselhorn
Keyword(s):  
Science Fiction ◽  
Emotional Reactions ◽  
Uncanny Valley ◽  
Human Beings ◽  
Human Likeness ◽  
Ancient Times ◽  
The One ◽  
High Degree ◽  
Literature And Film ◽  
Very High

The fact that we develop feelings towards androids, i.e., objects with a humanlike appearance, has fascinated people since ancient times. However, as a short survey of the topic in history, science fiction literature and film shows, our emotional reactions towards them are ambivalent. On the one hand, we can develop feelings of empathy almost as we do with real human beings; on the other hand, we feel repulsion or dyspathy when those creatures show a very high degree of human likeness. Recently, Japanese roboticist Masahiro Mori coined the term “uncanny valley” to refer to this effect. The aim of this essay is, first, to give an explanation as to why we feel empathy towards androids although we know that they do not have feelings themselves. This presupposes a perception-based concept of empathy which is going to be developed on the basis of some of Theodor Lipps’ ideas. The second question to be answered is why empathy with androids turns into dyspathy when they become very humanlike. As I will argue, this is due to a particular kind of interference between perception and the imagination when confronted with very humanlike objects. This makes androids quite special objects right at the divide between humans and non-humans. They are non-human, but we feel ill at ease when treating them as mere objects.

scholarly journals The Traditional Royal Court among the Bin Kanyok of Zaire

Afrika Focus ◽  
1989 ◽  
Vol 5 (1-2) ◽  
Author(s):  
Patrick Wymeersch
Keyword(s):  
Political System ◽  
Colonial Period ◽  
Political Organization ◽  
The Political ◽  
Political Systems ◽  
Royal Family ◽  
Royal Court ◽  
The One ◽  
High Degree ◽  
Very High

This description represents what was more or less an ideal conception of political organization and kingship before the colonial period. If the traditional systems of ruling still remain, the material symbolism of kingship disappeared mostly in the scene of daily life in the king's large capital. cLooking at the political organization, two seemingly contradictory features emerge. On the one hand, there are the politically quasi-independent lineages living in the villages. The chief or eldest of a lineage is at the same time chief of the whole village. On the other hand, there is the formal political organization, build on a hierarchical model and imposed from the top. This political system is notable for its very high degree of centralization, and especially for the strong authority and power of the divine king. For the purpose of government, the kingdom is divided into sub-districts, containing several villages of an area, districts and provinces. They all depend, in hierarchy,from the capital. The capital accommodates most of the members of the royal family, numerous wives and children from the king and the ministers. The king's compound, standing in the middle of the capital, is surrounded by afence. This compound is divided into four specific parts and contains several houses and the palace of the king. On both sides of the royal compound, there is a main street where the ministers and theirfamilies live.The king's person is surrounded by a number of taboos. No one could see him eat in his private kitchen.The principal problem in the political organization is that of the administering the rest of the Kanyok empire, of keeping as a political unit a population divided into autonomous lineages. The model that is followed is, in general, typical of the kingdoms of the southern savanna belt of Zaire. Therefore the structure is pyramidal: the king at the apex delegates his power and authority to the governors. Their position duplicates that of the king, but on a smaller scale. The king is assisted by his ministers to whom he assigned highly specific functions. The king still remains the main focus for all the Bin Kanyok.KEYWORDS : Bin Kanyok, royal court, traditional political systems, Zaire. 

Electron Microscopy in Molecular Biology

1967 ◽  
Vol 25 ◽  
pp. 2-3
Author(s):  
Cecil E. Hall
Keyword(s):  
Electron Microscopy ◽  
Molecular Biology ◽  
Noise Level ◽  
Molecular Structures ◽  
Material Structure ◽  
The Arts ◽  
Shadow Casting ◽  
Electron Image ◽  
High Degree ◽  
Very High

The visualization of organic macromolecules such as proteins, nucleic acids, viruses and virus components has reached its high degree of effectiveness owing to refinements and reliability of instruments and to the invention of methods for enhancing the structure of these materials within the electron image. The latter techniques have been most important because what can be seen depends upon the molecular and atomic character of the object as modified which is rarely evident in the pristine material. Structure may thus be displayed by the arts of positive and negative staining, shadow casting, replication and other techniques. Enhancement of contrast, which delineates bounds of isolated macromolecules has been effected progressively over the years as illustrated in Figs. 1, 2, 3 and 4 by these methods. We now look to the future wondering what other visions are waiting to be seen. The instrument designers will need to exact from the arts of fabrication the performance that theory has prescribed as well as methods for phase and interference contrast with explorations of the potentialities of very high and very low voltages. Chemistry must play an increasingly important part in future progress by providing specific stain molecules of high visibility, substrates of vanishing “noise” level and means for preservation of molecular structures that usually exist in a solvated condition.

A Low-Noise, High-Gain Quasi-Millimeter-Wave Receiver MMIC with a Very High Degree of Integration Using 3D-MMIC Technology

2011 ◽  
Vol E94-C (10) ◽  
pp. 1548-1556 ◽  
Author(s):  
Takana KAHO ◽  
Yo YAMAGUCHI ◽  
Kazuhiro UEHARA ◽  
Kiyomichi ARAKI
Keyword(s):  
Millimeter Wave ◽  
High Gain ◽  
Low Noise ◽  
High Degree ◽  
Very High ◽  
Millimeter Wave Receiver

El Prestige: comparativa de los regímenes internacionales de responsabilidad civil

2019 ◽  
Vol 37 (3) ◽  
pp. 31
Author(s):  
Raquel Fernández González ◽  
Marcos Íñigo Pérez Pérez
Keyword(s):  
Institutional Economics ◽  
Geographical Area ◽  
New Institutional Economics ◽  
Rigorous Analysis ◽  
Judicial Process ◽  
Main Research ◽  
Civil Responsibility ◽  
The One ◽  
High Degree ◽  
The Prestige

The return of institutions to the main research agenda has highlighted the importance of rules in economic analysis. The New Institutional Economics has allowed a better understanding of the case studies that concern different areas of knowledge, also the one concerning the management of natural resources. In this article, the institutional analysis focuses on the maritime domain, where two large civil liability regimes for pollution coexist (OPA 90-IMO), each in a different geographical area (United States - Europe). Therefore, a comparative analysis is made between the two large regimes of civil responsibility assignment applying them to the Prestige catastrophe. In this way, the allocation and distribution of responsibilities in the investigation and subsequent judicial process of the Prestige is compared with an alternative scenario in which the applicable compensation instruments are governed by the provisions of the Oil Polution Act of 1990 (OPA 90), in order to establish a rigorous analysis on the effects that the different norms can have in the same scenario. In the comparative established in the case of the Prestige, where the responsibilities were solved very slowly in a judicial process with high transaction costs, the application of rules governed by the OPA 90 would not count with such a high degree of imperfection. This is so, since by applying the preponderance of the evidence existing in OPA 90 there would be no mitigation for the presumed culprits. On the other hand, the agents involved in the sinking would not be limited only to the owner, but also that operators or shipowners would be responsible as well. In addition, the amount of compensation would increase when counting in the damage count the personal damages, the taxes without perceiving and the ecological damage caused in a broad sense, damages not computable in the IMO.

Relations between carbon removal rates, biofilm size and density of a novel anaerobic reactor: the inverse turbulent bed

2000 ◽  
Vol 41 (4-5) ◽  
pp. 253-260 ◽  
Author(s):  
P. Buffière ◽  
R. Moletta
Keyword(s):  
Removal Rate ◽  
Removal Rates ◽  
Carbon Removal ◽  
Biofilm Growth ◽  
Loading Rates ◽  
Biomass Activity ◽  
High Turbulence ◽  
The One ◽  
High Level ◽  
Very High

An anaerobic inverse turbulent bed, in which the biogas only ensures fluidisation of floating carrier particles, was investigated for carbon removal kinetics and for biofilm growth and detachment. The range of operation of the reactor was kept within 5 and 30 kgCOD· m−3· d−1, with Hydraulic Retention Times between 0.28 and 1 day. The carbon removal efficiency remained between 70 and 85%. Biofilm size were rather low (between 5 and 30 μm) while biofilm density reached very high values (over 80 kgVS· m−3). The biofilm size and density varied with increasing carbon removal rates with opposite trends; as biofilm size increases, its density decreases. On the one hand, biomass activity within the reactor was kept at a high level, (between 0.23 and 0.75 kgTOC· kgVS· d−1, i.e. between 0.6 and 1.85 kgCOD·kgVS · d−1).This result indicates that high turbulence and shear may favour growth of thin, dense and active biofilms. It is thus an interesting tool for biomass control. On the other hand, volatile solid detachment increases quasi linearly with carbon removal rate and the total amount of solid in the reactor levels off at high OLR. This means that detachment could be a limit of the process at higher organic loading rates.

scholarly journals Multi-Locus Selection and the Structure of Variation at the white Gene of Drosophila melanogaster

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 635-645 ◽  
Author(s):  
David A Kirby ◽  
Wolfgang Stephan
Keyword(s):  
Drosophila Melanogaster ◽  
White Gene ◽  
Transcriptional Unit ◽  
North American Population ◽  
Evolutionary Mechanisms ◽  
Locus Selection ◽  
Neutral Equilibrium ◽  
History Of ◽  
High Degree ◽  
Very High

Abstract We surveyed sequence variation and divergence for the entire 5972-bp transcriptional unit of the white gene in 15 lines of Drosophila melanogaster and one line of D. simulans. We found a very high degree of haplotypic structuring for the polymorphisms in the 3′ half of the gene, as opposed to the polymorphisms in the 5′ half. To determine the evolutionary mechanisms responsible for this pattern, we sequenced a 1612-bp segment of the white gene from an additional 33 lines of D. melanogaster from a European and a North American population. This 1612-bp segment encompasses an 834bp region of the white gene in which the polymorphisms form high frequency haplotypes that cannot be explained by a neutral equilibrium model of molecular evolution. The small number of recombinants in the 834bp region suggests epistatic selection as the cause of the haplotypic structuring, while an investigation of nucleotide diversity supports a directional selection hypothesis. A multi-locus selection model that combines features from both-hypotheses and takes the recent history of D. melanogaster into account may be the best explanation for these data.

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