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Chromosoma

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https://www.readbyqxmd.com/read/28233057/co-segregation-of-sex-chromosomes-in-the-male-black-widow-spider-latrodectus-mactans-araneae-theridiidae
#1
Jeffrey G Ault, Kristen D Felt, Ryan N Doan, Alexander O Nedo, Cassondra A Ellison, Leocadia V Paliulis
During meiosis I, homologous chromosomes join together to form bivalents. Through trial and error, bivalents achieve stable bipolar orientations (attachments) on the spindle that eventually allow the segregation of homologous chromosomes to opposite poles. Bipolar orientations are stable through tension generated by poleward forces to opposite poles. Unipolar orientations lack tension and are stereotypically not stable. The behavior of sex chromosomes during meiosis I in the male black widow spider Latrodectus mactans (Araneae, Theridiidae) challenges the principles governing such a scenario...
February 23, 2017: Chromosoma
https://www.readbyqxmd.com/read/28213686/the-iswi-remodeler-in-plants-protein-complexes-biochemical-functions-and-developmental-roles
#2
REVIEW
Dongjie Li, Jie Liu, Wu Liu, Guang Li, Zhongnan Yang, Peng Qin, Lin Xu
Imitation Switch (ISWI) is a member of the ATP-dependent chromatin remodeling factor family, whose members move or restructure nucleosomes using energy derived from ATP hydrolysis. ISWI proteins are conserved in eukaryotes and usually form complexes with DDT (DNA-binding homeobox and different transcription factors)-domain proteins. Here, we review recent research on ISWI in the model plant Arabidopsis thaliana (AtISWI). AtISWI forms complexes with AtDDT-domain proteins, many of which have domain structures that differ from those of DDT-domain proteins in yeast and animals...
February 17, 2017: Chromosoma
https://www.readbyqxmd.com/read/28190081/post-meiotic-b-chromosome-expulsion-during-spermiogenesis-in-two-grasshopper-species
#3
Josefa Cabrero, María Martín-Peciña, Francisco J Ruiz-Ruano, Ricardo Gómez, Juan Pedro M Camacho
Most supernumerary (B) chromosomes are parasitic elements carrying out an evolutionary arms race with the standard (A) chromosomes. A variety of weapons for attack and defense have evolved in both contending elements, the most conspicuous being B chromosome drive and A chromosome drive suppression. Here, we show for the first time that most microspermatids formed during spermiogenesis in two grasshopper species contain expulsed B chromosomes. By using DNA probes for B-specific satellite DNAs in Eumigus monticola and Eyprepocnemis plorans, and also 18S rDNA in the latter species, we were able to count the number of B chromosomes in standard spermatids submitted to fluorescence in situ hybridization, as well as visualizing B chromosomes inside most microspermatids...
February 11, 2017: Chromosoma
https://www.readbyqxmd.com/read/28101670/recombination-correlates-with-synaptonemal-complex-length-and-chromatin-loop-size-in-bovids-insights-into-mammalian-meiotic-chromosomal-organization
#4
Aurora Ruiz-Herrera, Miluse Vozdova, Jonathan Fernández, Hana Sebestova, Laia Capilla, Jan Frohlich, Covadonga Vara, Adrià Hernández-Marsal, Jaroslav Sipek, Terence J Robinson, Jiri Rubes
Homologous chromosomes exchange genetic information through recombination during meiosis, a process that increases genetic diversity, and is fundamental to sexual reproduction. In an attempt to shed light on the dynamics of mammalian recombination and its implications for genome organization, we have studied the recombination characteristics of 112 individuals belonging to 28 different species in the family Bovidae. In particular, we analyzed the distribution of RAD51 and MLH1 foci during the meiotic prophase I that serve, respectively, as proxies for double-strand breaks (DSBs) which form in early stages of meiosis and for crossovers...
January 18, 2017: Chromosoma
https://www.readbyqxmd.com/read/28084535/dna-methylation-is-dispensable-for-changes-in-global-chromatin-architecture-but-required-for-chromocentre-formation-in-early-stem-cell-differentiation
#5
Vahideh Hassan-Zadeh, Peter Rugg-Gunn, David P Bazett-Jones
Epiblast stem cells (EpiSCs), which are pluripotent cells isolated from early post-implantation mouse embryos (E5.5), show both similarities and differences compared to mouse embryonic stem cells (mESCs), isolated earlier from the inner cell mass (ICM) of the E3.5 embryo. Previously, we have observed that while chromatin is very dispersed in E3.5 ICM, compact chromatin domains and chromocentres appear in E5.5 epiblasts after embryo implantation. Given that the observed chromatin re-organization in E5.5 epiblasts coincides with an increase in DNA methylation, in this study, we aimed to examine the role of DNA methylation in chromatin re-organization during the in vitro conversion of ESCs to EpiSCs...
January 13, 2017: Chromosoma
https://www.readbyqxmd.com/read/27981360/erratum-to-3d-genomics-imposes-evolution-of-the-domain-model-of-eukaryotic-genome-organization
#6
Sergey V Razin, Yegor S Vassetzky
No abstract text is available yet for this article.
December 15, 2016: Chromosoma
https://www.readbyqxmd.com/read/27909815/homoeologous-recombination-in-the-presence-of-ph1-gene-in-wheat
#7
Dal-Hoe Koo, Wenxuan Liu, Bernd Friebe, Bikram S Gill
A crossover (CO) and its cytological signature, the chiasma, are major features of eukaryotic meiosis. The formation of at least one CO/chiasma between homologous chromosome pairs is essential for accurate chromosome segregation at the first meiotic division and genetic recombination. Polyploid organisms with multiple sets of homoeologous chromosomes have evolved additional mechanisms for the regulation of CO/chiasma. In hexaploid wheat (2n = 6× = 42), this is accomplished by pairing homoeologous (Ph) genes, with Ph1 having the strongest effect on suppressing homoeologous recombination and homoeologous COs...
December 1, 2016: Chromosoma
https://www.readbyqxmd.com/read/27882407/a-novel-system-for-correcting-large-scale-chromosomal-aberrations-ring-chromosome-correction-via-reprogramming-into-induced-pluripotent-stem-cell-ipsc
#8
REVIEW
Taehyun Kim, Kathleen Plona, Anthony Wynshaw-Boris
Approximately 1 in 500 newborns are born with chromosomal abnormalities that include trisomies, translocations, large deletions, and duplications. There is currently no therapeutic approach for correcting such chromosomal aberrations in vivo or in vitro. When we attempted to produce induced pluripotent stem cell (iPSC) models from patient-derived fibroblasts that contained ring chromosomes, we found that the ring chromosomes were eliminated and replaced by duplicated normal copies of chromosomes through a mechanism of uniparental isodisomy (Bershteyn et al...
November 23, 2016: Chromosoma
https://www.readbyqxmd.com/read/27858158/structure-of-centromere-chromatin-from-nucleosome-to-chromosomal-architecture
#9
REVIEW
Thomas Schalch, Florian A Steiner
The centromere is essential for the segregation of chromosomes, as it serves as attachment site for microtubules to mediate chromosome segregation during mitosis and meiosis. In most organisms, the centromere is restricted to one chromosomal region that appears as primary constriction on the condensed chromosome and is partitioned into two chromatin domains: The centromere core is characterized by the centromere-specific histone H3 variant CENP-A (also called cenH3) and is required for specifying the centromere and for building the kinetochore complex during mitosis...
November 17, 2016: Chromosoma
https://www.readbyqxmd.com/read/27837282/the-chromosomal-basis-of-meiotic-acentrosomal-spindle-assembly-and-function-in-oocytes
#10
REVIEW
Sarah J Radford, Alexandra L Nguyen, Karen Schindler, Kim S McKim
Several aspects of meiosis are impacted by the absence of centrosomes in oocytes. Here, we review four aspects of meiosis I that are significantly affected by the absence of centrosomes in oocyte spindles. One, microtubules tend to assemble around the chromosomes. Two, the organization of these microtubules into a bipolar spindle is directed by the chromosomes. Three, chromosome bi-orientation and attachment to microtubules from the correct pole require modification of the mechanisms used in mitotic cells. Four, chromosome movement to the poles at anaphase cannot rely on polar anchoring of spindle microtubules by centrosomes...
November 11, 2016: Chromosoma
https://www.readbyqxmd.com/read/27834006/centromere-repositioning-explains-fundamental-number-variability-in-the-new-world-monkey-genus-saimiri
#11
Giorgia Chiatante, Oronzo Capozzi, Marta Svartman, Polina Perelman, Lucy Centrone, Svetlana S Romanenko, Takafumi Ishida, Mirela Valeri, Melody E Roelke-Parker, Roscoe Stanyon
Cytogenetics has historically played a key role in research on squirrel monkey (genus Saimiri) evolutionary biology. Squirrel monkeys have a diploid number of 2n = 44, but vary in fundamental number (FN). Apparently, differences in FN have phylogenetic implications and are correlated with geographic regions. A number of hypothetical mechanisms were proposed to explain difference in FN: translocations, heterochromatin, or, most commonly, pericentric inversions. Recently, an additional mechanism, centromere repositioning, was discovered, which can alter chromosome morphology and FN...
November 10, 2016: Chromosoma
https://www.readbyqxmd.com/read/27796495/transcription-replication-conflicts-at-chromosomal-fragile-sites-consequences-in-m-phase-and-beyond
#12
REVIEW
Vibe H Oestergaard, Michael Lisby
Collision between the molecular machineries responsible for transcription and replication is an important source of genome instability. Certain transcribed regions known as chromosomal fragile sites are particularly prone to recombine and mutate in a manner that correlates with specific transcription and replication patterns. At the same time, these chromosomal fragile sites engage in aberrant DNA structures in mitosis. Here, we discuss the mechanistic details of transcription-replication conflicts including putative scenarios for R-loop-induced replication inhibition to understand how transcription-replication conflicts transition from S phase into various aberrant DNA structures in mitosis...
October 28, 2016: Chromosoma
https://www.readbyqxmd.com/read/27645892/centromeric-and-non-centromeric-satellite-dna-organisation-differs-in-holocentric-rhynchospora-species
#13
Tiago Ribeiro, André Marques, Petr Novák, Veit Schubert, André L L Vanzela, Jiri Macas, Andreas Houben, Andrea Pedrosa-Harand
Satellite DNA repeats (or satDNA) are fast-evolving sequences usually associated with condensed heterochromatin. To test whether the chromosomal organisation of centromeric and non-centromeric satDNA differs in species with holocentric chromosomes, we identified and characterised the major satDNA families in the holocentric Cyperaceae species Rhynchospora ciliata (2n = 10), R. globosa (2n = 50) and R. tenuis (2n = 2x = 4 and 2n = 4x = 8). While conserved centromeric repeats (present in R. ciliata and R...
September 19, 2016: Chromosoma
https://www.readbyqxmd.com/read/27638401/investigating-somatic-aneuploidy-in-the-brain-why-we-need-a-new-model
#14
REVIEW
Jimi L Rosenkrantz, Lucia Carbone
The steady occurrence of DNA mutations is a key source for evolution, generating the genomic variation in the population upon which natural selection acts. Mutations driving evolution have to occur in the oocytes and sperm in order to be transmitted to the next generation. Through similar mechanisms, mutations also accumulate in somatic cells (e.g., skin cells, neurons, lymphocytes) during development and adult life. The concept that somatic cells can collect new mutations with time suggests that we are a mosaic of cells with different genomic compositions...
September 16, 2016: Chromosoma
https://www.readbyqxmd.com/read/27631793/nuclear-morphologies-their-diversity-and-functional-relevance
#15
Benjamin M Skinner, Emma E P Johnson
Studies of chromosome and genome biology often focus on condensed chromatin in the form of chromosomes and neglect the non-dividing cells. Even when interphase nuclei are considered, they are often then treated as interchangeable round objects. However, different cell types can have very different nuclear shapes, and these shapes have impacts on cellular function; indeed, many pathologies are linked with alterations to nuclear shape. In this review, we describe some of the nuclear morphologies beyond the spherical and ovoid...
September 8, 2016: Chromosoma
https://www.readbyqxmd.com/read/27530342/holocentromere-identity-from-the-typical-mitotic-linear-structure-to-the-great-plasticity-of-meiotic-holocentromeres
#16
REVIEW
André Marques, Andrea Pedrosa-Harand
The centromere is the chromosomal site of kinetochore assembly and is responsible for the correct chromosome segregation during mitosis and meiosis in eukaryotes. Contrary to monocentrics, holocentric chromosomes lack a primary constriction, what is attributed to a kinetochore activity along almost the entire chromosome length during mitosis. This extended centromere structure imposes a problem during meiosis, since sister holocentromeres are not co-oriented during first meiotic division. Thus, regardless of the relatively conserved somatic chromosome structure of holocentrics, during meiosis holocentric chromosomes show different adaptations to deal with this condition...
September 2016: Chromosoma
https://www.readbyqxmd.com/read/26743516/the-cryptic-y-autosome-translocation-in-the-small-indian-mongoose-herpestes-auropunctatus-revealed-by-molecular-cytogenetic-approaches
#17
Chie Murata, Hirohito Sawaya, Katsushi Nakata, Fumio Yamada, Issei Imoto, Asato Kuroiwa
In initial studies of the eutherian small Indian mongoose (Herpestes auropunctatus), the Y chromosome could not be identified in somatic cells. The male chromosome number is uniquely odd, 2n = 35, whereas that of females is 2n = 36. Previous reports indicated that this unique karyotype resulted from a translocation of the ancestral Y chromosome to an autosome. However, it has been difficult to identify the chromosomes that harbor the translocated Y chromosomal segment because it is an extremely small euchromatic region...
September 2016: Chromosoma
https://www.readbyqxmd.com/read/26685999/formation-of-nup98-containing-nuclear-bodies-in-hela-sublines-is-linked-to-genomic-rearrangements-affecting-chromosome-11
#18
Serge Romana, Isabelle Radford-Weiss, Jean-Michel Lapierre, Valérie Doye, Marie-Claude Geoffroy
Nup98 is an important component of the nuclear pore complex (NPC) and also a rare but recurrent target for chromosomal translocation in leukaemogenesis. Nup98 contains multiple cohesive Gly-Leu-Phe-Gly (GLFG) repeats that are critical notably for the formation of intranuclear GLFG bodies. Previous studies have reported the existence of GLFG bodies in cells overexpressing exogenous Nup98 or in a HeLa subline (HeLa-C) expressing an unusual elevated amount of endogenous Nup98. Here, we have analysed the presence of Nup98-containing bodies in several human cell lines...
September 2016: Chromosoma
https://www.readbyqxmd.com/read/26685998/male-meiosis-in-crustacea-synapsis-recombination-epigenetics-and-fertility-in-daphnia-magna
#19
Rocío Gómez, Kay Van Damme, Jaime Gosálvez, Eugenio Sánchez Morán, John K Colbourne
We present the first detailed cytological study of male meiosis in Daphnia (Crustacea: Branchiopoda: Cladocera)-an aquatic microcrustacean with a cyclical parthenogenetic life cycle. Using immunostaining of the testes in Daphnia magna for baseline knowledge, we characterized the different stages of meiotic division and spermiogenesis in relation to the distribution of proteins involved in synapsis, early recombination events and sister chromatid cohesion. We also studied post-translational histone modifications in male spermatocytes, in relation to the dynamic chromatin progression of meiosis...
September 2016: Chromosoma
https://www.readbyqxmd.com/read/26667931/mapping-centromeres-of-microchromosomes-in-the-zebra-finch-taeniopygia-guttata-using-half-tetrad-analysis
#20
Ulrich Knief, Wolfgang Forstmeier
Centromeres usually consist of hundreds of kilobases of repetitive sequence which renders them difficult to assemble. As a consequence, centromeres are often missing from assembled genomes and their locations on physical chromosome maps have to be inferred from flanking sequences via fluorescence in situ hybridization (FISH). Alternatively, centromere positions can be mapped using linkage analyses in accidentally triploid individuals formed by half-tetrads (resulting from the inheritance of two chromatids from a single meiosis)...
September 2016: Chromosoma
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