scholarly journals Hexavalents in spermatocytes of Robertsonian heterozygotes between Mus m. domesticus 2n=26 from the Vulcano and Lipari Islands (Aeolian Archipelago, Italy)

2018 ◽  
Author(s):  
Soledad Berríos ◽  
Raúl Fernández-Donoso ◽  
Jesús Page ◽  
Eliana Ayarza ◽  
Ernesto Capanna ◽  
...  
Keyword(s):  
X Chromosome ◽  
Nuclear Architecture ◽  
Mus Musculus Domesticus ◽  
Open Chain ◽  
Telocentric Chromosome ◽  
Telocentric Chromosomes ◽  
Xy Bivalent ◽  
Chromosomal Changes ◽  
A Chain ◽  
Pachytene Spermatocytes

The size and shape of the chromosomes, as well as the chromosomal domains that compose them, are determinants in the distribution and interaction between the bivalents within the nucleus of spermatocytes in prophase I of meiosis. Thus the nuclear architecture characteristic of the karyotype of a species can be modified by chromosomal changes such as Rb chromosomes. In this study we analysed the meiotic prophase nuclear organization of the heterozygous spermatocytes from Mus musculus domesticus 2n=26, and the synaptic configuration of the hexavalent formed by the dependent Rb chromosomes Rbs 6.16, 16.10, 10.15, 15.17 and the telocentric chromosomes 6 and 17. Spreads of 88 pachytene spermatocytes from two males were studied and in all of them five metacentric bivalents, four telocentric bivalents, one hexavalent and the XY bivalent were observed. About 48% of the hexavalents formed a chain or a ring of synapsed chromosomes, the latter closed by synapsis between the short arms of telocentric chromosomes 6 and 17.  About 52% of hexavalents formed an open chain of 10 synapsed chromosomal arms belonging to 6 chromosomes.  In about half of the unsynapsed hexavalents one of the telocentric chromosome short arms appears associated with the X chromosome single axis, which was otherwise normally paired with the Y chromosome.  The cluster of pericentromeric heterochromatin mostly determines the hexavalent’s nuclear configuration, dragging the centromeric regions and all the chromosomes towards the nuclear envelope similar to an association of five telocentric bivalents. These reiterated encounters between these chromosomes restrict the interactions with other chromosomal domains and might favour eventual rearrangements within the metacentric, telocentric or hexavalent chromosome subsets. The unsynapsed short arms of telocentric chromosomes frequently bound to the single axis of the X chromosome could further complicate the already complex segregation of hexavalent chromosomes.

Study of Dosage Compensation in Drosophila

Genetics ◽  
2003 ◽  
Vol 165 (3) ◽  
pp. 1167-1181
Author(s):  
Pei-Wen Chiang ◽  
David M Kurnit
Keyword(s):  
Gene Expression ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Qpcr Assay ◽  
Male And Female ◽  
Multiple Genes ◽  
Chromosomal Changes ◽  
Regulatory Effects

Abstract Using a sensitive RT-QPCR assay, we analyzed the regulatory effects of sex and different dosage compensation mutations in Drosophila. To validate the assay, we showed that regulation for several genes indeed varied with the number of functional copies of that gene. We then confirmed that dosage compensation occurred for most genes we examined in male and female flies. Finally, we examined the effects on regulation of several genes in the MSL pathway, presumed to be involved in sex-dependent determination of regulation. Rather than seeing global alterations of either X chromosomal or autosomal genes, regulation of genes on either the X chromosome or the autosomes could be elevated, depressed, or unaltered between sexes in unpredictable ways for the various MSL mutations. Relative dosage for a given gene between the sexes could vary at different developmental times. Autosomal genes often showed deranged regulatory levels, indicating they were in pathways perturbed by X chromosomal changes. As exemplified by the BR-C locus and its dependent Sgs genes, multiple genes in a given pathway could exhibit coordinate regulatory modulation. The variegated pattern shown for expression of both X chromosomal and autosomal loci underscores the complexity of gene expression so that the phenotype of MSL mutations does not reflect only simple perturbations of genes on the X chromosome.

Alteration of nuclear architecture in male germ cells of chromosomally derived subfertile mice

2001 ◽  
Vol 114 (24) ◽  
pp. 4429-4434
Author(s):  
Silvia Garagna ◽  
Maurizio Zuccotti ◽  
Alan Thornhill ◽  
Raul Fernandez-Donoso ◽  
Soledad Berrios ◽  
...  
Keyword(s):  
Sertoli Cells ◽  
Spatial Organization ◽  
Nuclear Architecture ◽  
Spatial Arrangement ◽  
Cell Types ◽  
Condensed State ◽  
Germ Cell Differentiation ◽  
Y Chromosomes ◽  
Dual Colour ◽  
Pachytene Spermatocytes

The mammalian cell nucleus consists of numerous compartments involved in the regular unfolding of processes such as DNA replication and transcription, RNA maturation, protein synthesis and cell division. Knowledge is increasing of the relationships between high-order levels of chromatin organization and its spatial organization, and of how these relationships contribute to the various functions carried out in the nucleus. We have studied the spatial arrangement of mouse telocentric chromosomes 5, 11, 13, 15, 16 and 17, some of their metacentric Robertsonian derivatives, and X and Y chromosomes by whole chromosome painting in male germ (spermatogonia, pachytene spermatocytes and spermatids) and Sertoli cells of homozygous and heterozygous individuals. Using dual-colour fluorescence in situ hybridization we found that these chromosomes occupy specific nuclear territories in each cell type analysed. When chromosomes are present as Robertsonian metacentrics in the heterozygous state, that is, as Robertsonian metacentrics and their homologous telocentrics, differences in their nuclear positions are detectable: heterozygosity regularly produces a change in the nuclear position of one of the two homologous telocentrics in all the cell types studied. In the Robertsonian heterozygotes, the vast majority of the Sertoli cells show the sex chromosomes in a condensed state, whereas they appear decondensed in the Robertsonian homozygotes. As the Robertsonian heterozygosities we studied produce a chromosomally derived impairment of male germ-cell differentiation, we discuss the possibility that changes in chromosome spatial territories may alter some nuclear machinery (e.g., synapsis, differential gene expression) important for the correct unfolding of the meiotic process and for the proper functioning of Sertoli cells.

scholarly journals Studies on Metatherian Sex Chromosomes. IX. Sex Chromosomes of the Greater Glider (Marsupialia : Petauridae)

1979 ◽  
Vol 32 (3) ◽  
pp. 375 ◽  
Author(s):  
JD Murray ◽  
GM McKay ◽  
GB Sharman
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
National Park ◽  
Secondary Constriction ◽  
X Chromosomes ◽  
Cultured Fibroblasts ◽  
Multiple Sex Chromosomes ◽  
Eastern Australia ◽  
Xy Bivalent ◽  
Secondary Constrictions

The greater glider, currently but incorrectly known as Schoinobates vo/ans, is widely distributed in forested regions in eastern Australia. All animals studied from six different localities had 20 autosomes but there were four chromosomally distinct populations. At Royal National Park, N.S.W., all female greater gliders studied had 22 chromosomes including two large submetacentric X chromosomes with subterminal secondary constrictions in their longer arms. This form of X chromosome occurred also at Bondo State Forest, Myall Lakes and Coff's Harbour, N.S.W., and at Eidsvold, Qld. At Coomooboolaroo, Qld, the X chromosome was also a large submetacentric but a secondary constriction occurred in the shorter arm. Two chromosomally distinct types apparently occur in Royal National Park, one with XY m,ales as in all other populations, and one with XY1Y2 males. Y or Yb but not Y 2, chromosomes were eliminated from the bone marrow in all populations but were present in spermatogonia, primary sperrnatocytes and cultured fibroblasts. Animals from Bondo State Forest had three or more acrocentric or metacentric supernumerary chromosomes. [Other keywords: C-banding, eytotaxonomy, multiple sex chromosomes, XY bivalent.]

scholarly journals Sex chromosome configurations in pachytene spermatocytes of an XYY mouse

1990 ◽  
Vol 56 (2-3) ◽  
pp. 129-133 ◽  
Author(s):  
Charles Tease
Keyword(s):  
Sex Chromosomes ◽  
Male Mouse ◽  
Sex Chromosome ◽  
Chromosome Constitution ◽  
Sterile Male ◽  
Xy Bivalent ◽  
Pachytene Spermatocytes ◽  
Metaphase I

SummaryKaryotypic investigation of a phenotypically normal but sterile male mouse showed the presence of an XYY sex chromosome constitution. The synaptic behaviour of the three sex chromosomes was examined in 65 pachytene cells. The sex chromosomes formed a variety of synaptic configurations: an XYY trivalent (40%); an XY bivalent and Y univalent (38·5%); an X univalent and YY bivalent (13·8%); or X, Y, Y univalence (7·7%). There was considerable variation in the extent of synapsis and some of the associations clearly involved nonhomologous pairing. These observations have been compared with previously published information on chromosome configurations at metaphase I from other XYY males.

scholarly journals On Constraint Manifolds of Lorentz Sphere

2020 ◽  
Vol 28 (2) ◽  
pp. 15-34
Author(s):  
Buşra Aktaş ◽  
Olgun Durmaz ◽  
Hal˙t Gündoğan
Keyword(s):  
Lorentz Space ◽  
Structure Equation ◽  
Geometric Constructions ◽  
Open Chain ◽  
Constraint Manifold ◽  
Structure Equations ◽  
A Chain

AbstractThe expression of the structure equation of a mechanism is significant to present the last position of the mechanism. Moreover, in order to attain the constraint manifold of a chain, we need to constitute the structure equation. In this paper, we determine the structure equations and the constraint manifolds of a spherical open-chain in the Lorentz space. The structure equations of spherical open chain with reference to the causal character of the first link are obtained. Later, the constraint manifolds of the mechanism are determined by means of these equations. The geometric constructions corresponding to these manifolds are studied.

scholarly journals The oxidation of aromatic hydrocarbons at high pressures. I— Benzene. II— Toluene. III— Ethyl Benzene

1936 ◽  
Vol 153 (879) ◽  
pp. 448-462 ◽  
Keyword(s):  
Aromatic Hydrocarbons ◽  
High Pressures ◽  
Vapour Phase ◽  
Complete Analysis ◽  
Ethyl Benzene ◽  
Open Chain ◽  
Slow Combustion ◽  
Benzene Toluene ◽  
A Chain ◽  
Oxidation Of Benzene

It has been shown in previous papers of this series that during the slow combustion of the aliphatic hydrocarbons at high pressure conditions are particularly favourable to the isolation of the intermediate compounds involved, and that such oxidations take place by successive stages of hydroxylation. The work has now been extended to include the aromatic hydrocarbons, and the present paper embodies the results for benzene, toluene, and ethyl benzene. The homogeneous slow oxidation of benzene in the vapour phase has been studied by Fort and Hinshelwood, who concluded that at atmospheric pressure it proceeds by a chain mechanism somewhat analogous to that which they postulated for ethylene. Although a complete analysis of the products of combustion was not made, other circumstances suggested that during an "apparent period of induction" the first products were formed without pressure increase, and that, to quote their words, 'hydroxylation of the double bonds may be assumed to occur, followed by rapid further oxidation of the open chain unsaturated compound so produced to a substance like glyoxal. The remaining stages would then be analagous to the oxidation of acetylene

scholarly journals Homoeologous pairing of a chromosome from Agropyron elongatum with those of Triticum aestivum and Aegilops speltoides

1967 ◽  
Vol 10 (1) ◽  
pp. 63-71 ◽  
Author(s):  
Roy Johnson ◽  
Gordon Kimber
Keyword(s):  
Triticum Aestivum ◽  
Average Rate ◽  
Aegilops Speltoides ◽  
Homoeologous Pairing ◽  
Agropyron Elongatum ◽  
Telocentric Chromosome ◽  
Telocentric Chromosomes ◽  
Group 6 ◽  
Genetic Compensation ◽  
Homoeologous Chromosomes

1. Complex hybrids were produced having twenty-nine chromosomes, consisting of one telocentric and twenty complete chromosomes of T. aestivum (2n = 6x = 42), seven complete chromosomes of Ae. speltoides (2n = 2x = 14) and one telocentric chromosome derived from A. elongatum (2n = 10x = 70). The presence of the Ae. speltoides genome permitted pairing between homoeologous chromosomes at meiosis and the behaviour of the two telocentric chromosomes was observed.2. The A. elongatum chromosome was seen to pair with chromosomes homoeologous to those of group 6. There was no evidence that it paired with chromosomes of any other group.3. When the A. elongatum telocentric and those of 6A and 6D occurred in the same configuration it was evident that the telocentrics 6A and 6D were for corresponding chromosome arms, and the A. elongatum telocentric for the opposite arm.4. The average rate of pairing was much lower for the A. elongatum telocentric than for wheat telocentrics. Previous studies had indicated very good genetic compensation of the A. elongatum chromosome for chromosomes 6A and 6D. It was therefore indicated that genetic equivalence and pairing affinity were not closely related in this case. Some implications of this are discussed.

scholarly journals Construction and behavior of circularly permuted and telocentric chromosomes in Saccharomyces cerevisiae.

1986 ◽  
Vol 6 (9) ◽  
pp. 3166-3172 ◽  
Author(s):  
A W Murray ◽  
J W Szostak
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Very High Frequency ◽  
Telocentric Chromosome ◽  
Artificial Chromosomes ◽  
Telocentric Chromosomes ◽  
Novel Variants ◽  
Chromosome Iii ◽  
And Behavior ◽  
Mitosis And Meiosis ◽  
Very High

We developed techniques that allow us to construct novel variants of Saccharomyces cerevisiae chromosomes. These modified chromosomes have precisely determined structures. A metacentric derivative of chromosome III which lacks the telomere-associated X and Y' elements, which are found at the telomeres of most yeast chromosomes, behaves normally in both mitosis and meiosis. We made a circularly permuted telocentric version of yeast chromosome III whose closest telomere was 33 kilobases from the centromere. This telocentric chromosome was lost at a frequency of 1.6 X 10(-5) per cell compared with a frequency of 4.0 X 10(-6) for the natural metacentric version of chromosome III. An extremely telocentric chromosome whose closet telomere was only 3.5 kilobases from the centromere was lost at a frequency of 6.0 X 10(-5). The mitotic stability of telocentric chromosomes shows that the very high frequency of nondisjunction observed for short linear artificial chromosomes is not due to inadequate centromere-telomere separation.

scholarly journals Size threshold for Saccharomyces cerevisiae chromosomes: generation of telocentric chromosomes from an unstable minichromosome.

1986 ◽  
Vol 6 (3) ◽  
pp. 925-932 ◽  
Author(s):  
V A Zakian ◽  
H M Blanton ◽  
L Wetzel ◽  
G M Dani
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Telocentric Chromosome ◽  
Stable Transformants ◽  
Large Deletions ◽  
Telocentric Chromosomes ◽  
Orthogonal Field ◽  
The Right ◽  
Linear Chromosomes ◽  
Size Threshold

A 9-kilobase pair CEN4 linear minichromosome constructed in vitro transformed Saccharomyces cerevisiae with high frequency but duplicated or segregated inefficiently in most cells. Stable transformants were only produced by events which fundamentally altered the structure of the minichromosome: elimination of telomeres, alteration of the centromere, or an increase of fivefold or greater in its size. Half of the stable transformants arose via homologous recombination between an intact chromosome IV and the CEN4 minichromosome. This event generated a new chromosome from each arm of chromosome IV. The other "arm" of each new chromosome was identical to one "arm" of the unstable minichromosome. Unlike natural yeast chromosomes, these new chromosomes were telocentric: their centromeres were either 3.9 or 5.4 kilobases from one end of the chromosome. The mitotic stability of the telocentric chromosome derived from the right arm of chromosome IV was determined by a visual assay and found to be comparable to that of natural yeast chromosomes. Both new chromosomes duplicated, paired, and segregated properly in meiosis. Moreover, their structure, as deduced from mobilities in orthogonal field gels, did not change with continued mitotic growth or after passage through meiosis, indicating that they did not give rise to isochromosomes or suffer large deletions or additions. Thus, in S. cerevisiae the close spacing of centromeres and telomeres on a DNA molecule of chromosomal size does not markedly alter the efficiency with which it is maintained. Taken together these data suggest that there is a size threshold below which stable propagation of linear chromosomes is no longer possible.

Controllable supramolecular polymerization via a chain-growth mechanism

2018 ◽  
Vol 54 (8) ◽  
pp. 928-931 ◽  
Author(s):  
Deep Sankar Pal ◽  
Haridas Kar ◽  
Suhrit Ghosh
Keyword(s):  
Carboxylic Acid ◽  
Sample Preparation ◽  
Growth Mechanism ◽  
Preparation Method ◽  
Chain Growth ◽  
Sample Preparation Method ◽  
Open Chain ◽  
Naphthalene Diimide ◽  
A Chain ◽  
Supramolecular Polymerization

A naphthalene-diimide appended carboxylic acid either spontaneously self-assembles (P) by an open-chain H-bonding or can be arrested in an intra-molecularly H-bonded monomeric state (M) depending on the sample preparation method. Living supramoleular polymerization of M can be initiated by a seed, generated from P.

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