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Chromosoma

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https://www.readbyqxmd.com/read/27909815/homoeologous-recombination-in-the-presence-of-ph1-gene-in-wheat
#1
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
#2
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
#3
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
#4
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
#5
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
#6
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
#7
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
#8
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
#9
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
#10
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/27411693/evolutionary-plasticity-of-acipenseriform-genomes
#11
REVIEW
Vladimir A Trifonov, Svetlana S Romanenko, Violetta R Beklemisheva, Larisa S Biltueva, Alexey I Makunin, Natalia A Lemskaya, Anastasia I Kulemzina, Roscoe Stanyon, Alexander S Graphodatsky
Acipenseriformes is an order of ray-finned fishes, comprising 27 extant species of sturgeons and paddlefishes inhabiting waters of the Northern Hemisphere. The order has a basal position within Actinopteri (ray-finned fish minus polypterids) and is characterized by many specific morphological and genomic features, including high diploid chromosome numbers, various levels of ploidy between species, unclear sex determination, and propensity to interspecific hybridization. Recent advances in molecular genetics, genomics, and comparative cytogenetics produced novel data on different aspects of acipenseriform biology, including improved phylogenetic reconstructions and better understanding of genome structure...
September 2016: Chromosoma
https://www.readbyqxmd.com/read/27376724/kinetochore-assembly-and-function-through-the-cell-cycle
#12
REVIEW
Harsh Nagpal, Tatsuo Fukagawa
The kinetochore is an essential structure for the chromosome segregation machinery in eukaryotes; it serves as a bridge between the spindle microtubules and chromosomes. The kinetochore consists of multiple interconnecting components on the centromere; therefore, understanding its formation, molecular function, and regulation has remained an ongoing challenge. Recent studies have provided new insights into centromere identity, kinetochore assembly, and function. In this review, we discuss recent advances in our understanding of the function and regulation of key kinetochore components...
September 2016: Chromosoma
https://www.readbyqxmd.com/read/27255308/marsupials-as-models-for-understanding-the-role-of-chromosome-rearrangements-in-evolution-and-disease
#13
REVIEW
Janine E Deakin, Maya Kruger-Andrzejewska
Chromosome rearrangements have been implicated in diseases, such as cancer, and speciation, but it remains unclear whether rearrangements are causal or merely a consequence of these processes. Two marsupial families with very different rates of karyotype evolution provide excellent models in which to study the role of chromosome rearrangements in a disease and evolutionary context. The speciose family Dasyuridae displays remarkable karyotypic conservation, with all species examined to date possessing nearly identical karyotypes...
September 2016: Chromosoma
https://www.readbyqxmd.com/read/27153833/the-legacy-of-drosophila-imaginal-discs
#14
REVIEW
Jorge V Beira, Renato Paro
The study of Drosophila imaginal discs has contributed to a number of discoveries in developmental and cellular biology. In addition to the elucidation of the role of tissue compartments and organ-specific master regulator genes during development, imaginal discs have also become well established as models for studying cellular interactions and complex genetic pathways. Here, we review key discoveries resulting from investigations of these epithelial precursor organs, ranging from cell fate determination and transdetermination to tissue patterning...
September 2016: Chromosoma
https://www.readbyqxmd.com/read/27116033/transformation-associated-recombination-tar-cloning-for-genomics-studies-and-synthetic-biology
#15
REVIEW
Natalay Kouprina, Vladimir Larionov
Transformation-associated recombination (TAR) cloning represents a unique tool for isolation and manipulation of large DNA molecules. The technique exploits a high level of homologous recombination in the yeast Sacharomyces cerevisiae. So far, TAR cloning is the only method available to selectively recover chromosomal segments up to 300 kb in length from complex and simple genomes. In addition, TAR cloning allows the assembly and cloning of entire microbe genomes up to several Mb as well as engineering of large metabolic pathways...
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
#16
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/26728621/resetting-a-functional-g1-nucleus-after-mitosis
#17
REVIEW
Ines J de Castro, Ezgi Gokhan, Paola Vagnarelli
The maintenance of the correct cellular information goes beyond the simple transmission of an intact genetic code from one generation to the next. Epigenetic changes, topological cues and correct protein-protein interactions need to be re-established after each cell division to allow the next cell cycle to resume in the correct regulated manner. This process begins with mitotic exit and re-sets all the changes that occurred during mitosis thus restoring a functional G1 nucleus in preparation for the next cell cycle...
September 2016: Chromosoma
https://www.readbyqxmd.com/read/26728620/the-upstreams-and-downstreams-of-h3k79-methylation-by-dot1l
#18
REVIEW
Hanneke Vlaming, Fred van Leeuwen
Histone modifications regulate key processes of eukaryotic genomes. Misregulation of the enzymes that place these modifications can lead to disease. An example of this is DOT1L, the enzyme that can mono-, di-, and trimethylate the nucleosome core on lysine 79 of histone H3 (H3K79). DOT1L plays a role in development and its misregulation has been implicated in several cancers, most notably leukemias caused by a rearrangement of the MLL gene. A DOT1L inhibitor is in clinical trials for these leukemias and shows promising results, yet we are only beginning to understand DOT1L's function and regulation in the cell...
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
#19
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
#20
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
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