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1
Tamang, Sonam. "Principles and Applications of Fetal Chromosome Number and Structure Analysis". Sriwijaya Journal of Obstetrics and Gynecology 1, n. 2 (20 dicembre 2023): 39–43. http://dx.doi.org/10.59345/sjog.v1i2.83.
Testo completoAbstract (sommario):
A crucial diagnostic technique employed in prenatal diagnosis is examining the quantity and arrangement of fetal chromosomes. The fundamental premise of this study is to determine the chromosomal count in the fetal cells and detect any genetic or chromosomal abnormalities that may be present. A total of 46 chromosomes are typically present in the human body, organized into 23 pairs. These pairs include one pair of sex chromosomes and 22 pairs of autosomal chromosomes. This study enables the identification of chromosomal abnormalities, such as trisomy (the presence of an additional chromosome) and monosomy (the absence of a chromosome), which can have an impact on the health of the fetus. In addition to determining the number of chromosomes, this examination can also detect structural chromosome abnormalities like translocations, deletions, and duplications, which might potentially affect the health of the fetus. This investigation's findings provide significant insights to both patients and clinicians, enabling them to make more informed choices about continuing the pregnancy and receiving appropriate medical attention if genetic abnormalities are detected. This study can also be utilized for the identification of particular genetic illnesses associated with specific gene mutations, thereby aiding in treatment strategizing and postnatal readiness.
2
Gasser, Susan M. "Chromosome Structure: Coiling up chromosomes". Current Biology 5, n. 4 (aprile 1995): 357–60. http://dx.doi.org/10.1016/s0960-9822(95)00071-6.
Testo completo
3
Eidelman, Yuri, Ilya Salnikov, Svetlana Slanina e Sergey Andreev. "Chromosome Folding Promotes Intrachromosomal Aberrations under Radiation- and Nuclease-Induced DNA Breakage". International Journal of Molecular Sciences 22, n. 22 (10 novembre 2021): 12186. http://dx.doi.org/10.3390/ijms222212186.
Testo completoAbstract (sommario):
The long-standing question in radiation and cancer biology is how principles of chromosome organization impact the formation of chromosomal aberrations (CAs). To address this issue, we developed a physical modeling approach and analyzed high-throughput genomic data from chromosome conformation capture (Hi-C) and translocation sequencing (HTGTS) methods. Combining modeling of chromosome structure and of chromosomal aberrations induced by ionizing radiation (IR) and nuclease we made predictions which quantitatively correlated with key experimental findings in mouse chromosomes: chromosome contact maps, high frequency of cis-translocation breakpoints far outside of the site of nuclease-induced DNA double-strand breaks (DSBs), the distinct shape of breakpoint distribution in chromosomes with different 3D organizations. These correlations support the heteropolymer globule principle of chromosome organization in G1-arrested pro-B mouse cells. The joint analysis of Hi-C, HTGTS and physical modeling data offers mechanistic insight into how chromosome structure heterogeneity, globular folding and lesion dynamics drive IR-recurrent CAs. The results provide the biophysical and computational basis for the analysis of chromosome aberration landscape under IR and nuclease-induced DSBs.
4
Matsunaga, Sachihiro, e Kiichi Fukui. "The chromosome peripheral proteins play an active role in chromosome dynamics". BioMolecular Concepts 1, n. 2 (1 agosto 2010): 157–64. http://dx.doi.org/10.1515/bmc.2010.018.
Testo completoAbstract (sommario):
AbstractThe chromosome periphery is a chromosomal structure that covers the surface of mitotic chromosomes. The structure and function of the chromosome periphery has been poorly understood since its first description in 1882. It has, however, been proposed to be an insulator or barrier to protect chromosomes from subcellular substances and to act as a carrier of nuclear and nucleolar components to direct their equal distribution to daughter cells because most chromosome peripheral proteins (CPPs) are derived from the nucleolus or nucleus. Until now, more than 30 CPPs were identified in mammalians. Recent immunostaining analyses of CPPs have revealed that the chromosome periphery covers the centromeric region of mitotic chromosomes in addition to telomeres and regions between two sister chromatids. Knockdown analyses of CPPs using RNAi have revealed functions in chromosome dynamics, including cohesion of sister chromatids, kinetochore-microtubule attachments, spindle assembly and chromosome segregation. Because most CPPs are involved in various subcellular events in the nucleolus or nuclear at interphase, a temporal and spatial-specific knockdown method of CPPs in the chromosome periphery will be useful to understand the function of chromosome periphery in cell division.
5
Spell, R. M., e C. Holm. "Nature and distribution of chromosomal intertwinings in Saccharomyces cerevisiae". Molecular and Cellular Biology 14, n. 2 (febbraio 1994): 1465–76. http://dx.doi.org/10.1128/mcb.14.2.1465-1476.1994.
Testo completoAbstract (sommario):
To elucidate yeast chromosome structure and behavior, we examined the breakage of entangled chromosomes in DNA topoisomerase II mutants by hybridization to chromosomal DNA resolved by pulsed-field gel electrophoresis. Our study reveals that large and small chromosomes differ in the nature and distribution of their intertwinings. Probes to large chromosomes (450 kb or larger) detect chromosome breakage, but probes to small chromosomes (380 kb or smaller) reveal no breakage products. Examination of chromosomes with one small arm and one large arm suggests that the two arms behave independently. The acrocentric chromosome XIV breaks only on the long arm, and its preferred region of breakage is approximately 200 kb from the centromere. When the centromere of chromosome XIV is relocated, the preferred region of breakage shifts accordingly. These results suggest that large chromosomes break because they have long arms and small chromosomes do not break because they have small arms. Indeed, a small metacentric chromosome can be made to break if it is rearranged to form a telocentric chromosome with one long arm or a ring with an "infinitely" long arm. These results suggest a model of chromosomal intertwining in which the length of the chromosome arm prevents intertwinings from passively resolving off the end of the arm during chromosome segregation.
6
Spell, R. M., e C. Holm. "Nature and distribution of chromosomal intertwinings in Saccharomyces cerevisiae." Molecular and Cellular Biology 14, n. 2 (febbraio 1994): 1465–76. http://dx.doi.org/10.1128/mcb.14.2.1465.
Testo completoAbstract (sommario):
To elucidate yeast chromosome structure and behavior, we examined the breakage of entangled chromosomes in DNA topoisomerase II mutants by hybridization to chromosomal DNA resolved by pulsed-field gel electrophoresis. Our study reveals that large and small chromosomes differ in the nature and distribution of their intertwinings. Probes to large chromosomes (450 kb or larger) detect chromosome breakage, but probes to small chromosomes (380 kb or smaller) reveal no breakage products. Examination of chromosomes with one small arm and one large arm suggests that the two arms behave independently. The acrocentric chromosome XIV breaks only on the long arm, and its preferred region of breakage is approximately 200 kb from the centromere. When the centromere of chromosome XIV is relocated, the preferred region of breakage shifts accordingly. These results suggest that large chromosomes break because they have long arms and small chromosomes do not break because they have small arms. Indeed, a small metacentric chromosome can be made to break if it is rearranged to form a telocentric chromosome with one long arm or a ring with an "infinitely" long arm. These results suggest a model of chromosomal intertwining in which the length of the chromosome arm prevents intertwinings from passively resolving off the end of the arm during chromosome segregation.
7
Uchida, Tetsuya, Naoto Ishihara, Hiroyuki Zenitani, Keiichiro Hiratsu e Haruyasu Kinashi. "Circularized Chromosome with a Large Palindromic Structure in Streptomyces griseus Mutants". Journal of Bacteriology 186, n. 11 (1 giugno 2004): 3313–20. http://dx.doi.org/10.1128/jb.186.11.3313-3320.2004.
Testo completoAbstract (sommario):
ABSTRACT Streptomyces linear chromosomes display various types of rearrangements after telomere deletion, including circularization, arm replacement, and amplification. We analyzed the new chromosomal deletion mutants Streptomyces griseus 301-22-L and 301-22-M. In these mutants, chromosomal arm replacement resulted in long terminal inverted repeats (TIRs) at both ends; different sizes were deleted again and recombined inside the TIRs, resulting in a circular chromosome with an extremely large palindrome. Short palindromic sequences were found in parent strain 2247, and these sequences might have played a role in the formation of this unique structure. Dynamic structural changes of Streptomyces linear chromosomes shown by this and previous studies revealed extraordinary strategies of members of this genus to keep a functional chromosome, even if it is linear or circular.
8
Pelttari, Jeanette, Mary-Rose Hoja, Li Yuan, Jian-Guo Liu, Eva Brundell, Peter Moens, Sabine Santucci-Darmanin et al. "A Meiotic Chromosomal Core Consisting of Cohesin Complex Proteins Recruits DNA Recombination Proteins and Promotes Synapsis in the Absence of an Axial Element in Mammalian Meiotic Cells". Molecular and Cellular Biology 21, n. 16 (15 agosto 2001): 5667–77. http://dx.doi.org/10.1128/mcb.21.16.5667-5677.2001.
Testo completoAbstract (sommario):
ABSTRACT The behavior of meiotic chromosomes differs in several respects from that of their mitotic counterparts, resulting in the generation of genetically distinct haploid cells. This has been attributed in part to a meiosis-specific chromatin-associated protein structure, the synaptonemal complex. This complex consist of two parallel axial elements, each one associated with a pair of sister chromatids, and a transverse filament located between the synapsed homologous chromosomes. Recently, a different protein structure, the cohesin complex, was shown to be associated with meiotic chromosomes and to be required for chromosome segregation. To explore the functions of the two different protein structures, the synaptonemal complex and the cohesin complex, in mammalian male meiotic cells, we have analyzed how absence of the axial element affects early meiotic chromosome behavior. We find that the synaptonemal complex protein 3 (SCP3) is a main determinant of axial-element assembly and is required for attachment of this structure to meiotic chromosomes, whereas SCP2 helps shape the in vivo structure of the axial element. We also show that formation of a cohesin-containing chromosomal core in meiotic nuclei does not require SCP3 or SCP2. Our results also suggest that the cohesin core recruits recombination proteins and promotes synapsis between homologous chromosomes in the absence of an axial element. A model for early meiotic chromosome pairing and synapsis is proposed.
9
Anderson, Lorinda K., Naser Salameh, Hank W. Bass, Lisa C. Harper, W. Z. Cande, Gerd Weber e Stephen M. Stack. "Integrating Genetic Linkage Maps With Pachytene Chromosome Structure in Maize". Genetics 166, n. 4 (1 aprile 2004): 1923–33. http://dx.doi.org/10.1093/genetics/166.4.1923.
Testo completoAbstract (sommario):
Abstract Genetic linkage maps reveal the order of markers based on the frequency of recombination between markers during meiosis. Because the rate of recombination varies along chromosomes, it has been difficult to relate linkage maps to chromosome structure. Here we use cytological maps of crossing over based on recombination nodules (RNs) to predict the physical position of genetic markers on each of the 10 chromosomes of maize. This is possible because (1) all 10 maize chromosomes can be individually identified from spreads of synaptonemal complexes, (2) each RN corresponds to one crossover, and (3) the frequency of RNs on defined chromosomal segments can be converted to centimorgan values. We tested our predictions for chromosome 9 using seven genetically mapped, single-copy markers that were independently mapped on pachytene chromosomes using in situ hybridization. The correlation between predicted and observed locations was very strong (r2 = 0.996), indicating a virtual 1:1 correspondence. Thus, this new, high-resolution, cytogenetic map enables one to predict the chromosomal location of any genetically mapped marker in maize with a high degree of accuracy. This novel approach can be applied to other organisms as well.
10
Wolf, Klaus Werner, Karel Novák e František Marec. "Chromosome structure in spermatogenesis of Anabolia furcata (Trichoptera)". Genome 35, n. 1 (1 febbraio 1992): 46–52. http://dx.doi.org/10.1139/g92-008.
Testo completoAbstract (sommario):
The structure of metaphase chromosomes was analysed in spermatogonia and spermatocytes of the caddis-fly, Anabolia furcata (Trichoptera: Limnephilidae), using ultrathin serial sections and electron microscopy. In metaphase spermatogonia, about 40% of the chromosomal length was covered with a compact kinetochore plate. Subjectively estimated, secondary spermatocytes were not significantly different in this respect. However, in primary spermatocytes, each bivalent showed four kinetochores, two at each poleward surface, connected with the chromosome. The kinetochores were not located at the chromosome portions most proximal to the spindle poles, but attached laterally in a more equatorial position. When the orientation of individual kinetochore plates in metaphase I bivalents was not roughly at right angles with respect to the spindle axis, gaps and holes were visible in the plates. This possibly indicates the presence of compound kinetochores in A. furcata. The center of the bivalents contains less dense material than the periphery. The structural features of chromosomes in this Trichoptera species are very similar to those described in Lepidotera species with a comparable chromosome number. Taken together with similarities in other karyotype characteristics, such as female heterogamety and the lack of chiasmata in female meiosis, this further corroborates the notion that Lepidoptera and Trichoptera have strong phylogenetic affinities.Key words: caddis-fly, metaphase chromosomes, kinetochore, microtubules, spindle.
11
Hołówka, Joanna, e Małgorzata Płachetka. "Structure of bacterial chromosome: An analysis of DNA-protein interactions in vivo". Postępy Higieny i Medycyny Doświadczalnej 71 (8 dicembre 2017): 0. http://dx.doi.org/10.5604/01.3001.0010.6696.
Testo completoAbstract (sommario):
According to recent reports, bacterial chromosomes exhibit a hierarchical organization. The number of proteins that bind DNA are responsible for local and global organization of the DNA ensuring proper chromosome compaction. Advanced molecular biology techniques combined with high-throughput DNA sequencing methods allow a precise analysis of bacterial chromosome structures on a local and global scale. Methods such as in vivo footprinting and ChIP-seq allow to map binding sites of analyzed proteins in certain chromosomal regions or along the whole chromosome while analysis of the spatial interactions on global scale could be performed by 3C techniques. Additional insight into complex structures created by chromosome-organizing proteins is provided by high-resolution fluorescence microscopy techniques.
12
Albert, Patrice S., Tao Zhang, Kassandra Semrau, Jean-Marie Rouillard, Yu-Hsin Kao, Chung-Ju Rachel Wang, Tatiana V. Danilova, Jiming Jiang e James A. Birchler. "Whole-chromosome paints in maize reveal rearrangements, nuclear domains, and chromosomal relationships". Proceedings of the National Academy of Sciences 116, n. 5 (17 gennaio 2019): 1679–85. http://dx.doi.org/10.1073/pnas.1813957116.
Testo completoAbstract (sommario):
Whole-chromosome painting probes were developed for each of the 10 chromosomes of maize by producing amplifiable libraries of unique sequences of oligonucleotides that can generate labeled probes through transcription reactions. These paints allow identification of individual homologous chromosomes for many applications as demonstrated in somatic root tip metaphase cells, in the pachytene stage of meiosis, and in interphase nuclei. Several chromosomal aberrations were examined as proof of concept for study of various rearrangements using probes that cover the entire chromosome and that label diverse varieties. The relationship of the supernumerary B chromosome and the normal chromosomes was examined with the finding that there is no detectable homology between any of the normal A chromosomes and the B chromosome. Combined with other chromosome-labeling techniques, a complete set of whole-chromosome oligonucleotide paints lays the foundation for future studies of the structure, organization, and evolution of genomes.
13
Dooner, H. K., e A. Belachew. "Chromosome breakage by pairs of closely linked transposable elements of the Ac-Ds family in maize." Genetics 129, n. 3 (1 novembre 1991): 855–62. http://dx.doi.org/10.1093/genetics/129.3.855.
Testo completoAbstract (sommario):
Abstract Chromosome breaks and hence chromosomal rearrangements often occur in maize stocks harboring transposable elements (TEs), yet it is not clear what types of TE structures promote breakage. We have shown previously that chromosomes containing a complex transposon structure consisting of an Ac (Activator) element closely linked in direct orientation to a terminally deleted or fractured Ac (fAc) element have a strong tendency to break during endosperm development. Here we show that pairs of closely linked transposons with intact ends, either two Ac elements--a common product of Ac transposition--or an Ac and a Ds (Dissociation) element, can constitute chromosome-breaking structures, and that the frequency of breakage is inversely related to intertransposon distance. Similar structures may also be implicated in chromosome breaks in other eukaryotic TE systems known to produce chromosomal rearrangements. The present findings are discussed in light of a model of chromosome breakage that is based on the transposition of a partially replicated macrotransposon delimited by the outside ends of the two linked TEs.
14
Machado, Cristina, Claudio E. Sunkel e Deborah J. Andrew. "Human Autoantibodies Reveal Titin as a Chromosomal Protein". Journal of Cell Biology 141, n. 2 (20 aprile 1998): 321–33. http://dx.doi.org/10.1083/jcb.141.2.321.
Testo completoAbstract (sommario):
Assembly of the higher-order structure of mitotic chromosomes is a prerequisite for proper chromosome condensation, segregation and integrity. Understanding the details of this process has been limited because very few proteins involved in the assembly of chromosome structure have been discovered. Using a human autoimmune scleroderma serum that identifies a chromosomal protein in human cells and Drosophila embryos, we cloned the corresponding Drosophila gene that encodes the homologue of vertebrate titin based on protein size, sequence similarity, developmental expression and subcellular localization. Titin is a giant sarcomeric protein responsible for the elasticity of striated muscle that may also function as a molecular scaffold for myofibrillar assembly. Molecular analysis and immunostaining with antibodies to multiple titin epitopes indicates that the chromosomal and muscle forms of titin may vary in their NH2 termini. The identification of titin as a chromosomal component provides a molecular basis for chromosome structure and elasticity.
15
Dwiranti, Astari, Hideaki Takata e Kiichi Fukui. "Reversible Changes of Chromosome Structure upon Different Concentrations of Divalent Cations". Microscopy and Microanalysis 25, n. 3 (17 aprile 2019): 817–21. http://dx.doi.org/10.1017/s1431927619000266.
Testo completoAbstract (sommario):
AbstractThe structural details of chromosomes have been of interest to researchers for many years, but how the metaphase chromosome is constructed remains unsolved. Divalent cations have been suggested to be required for the organization of chromosomes. However, detailed information about the role of these cations in chromosome organization is still limited. In the current study, we investigated the effects of Ca2+ and Mg2+ depletion and the reversibility upon re-addition of one of the two ions. Human chromosomes were treated with different concentrations of Ca2+and Mg2+. Depletion of Ca2+ and both Ca2+ and Mg2+ were carried out using 1, 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and ethylenediaminetetraacetic acid (EDTA), respectively. Chromosome structure was examined by fluorescence microscopy and scanning electron microscopy. The results indicated that chromosome structures after treatment with a buffer without Mg2+, after Ca2+ depletion, as well as after depletion of both Mg2+, and Ca2+, yielded fewer compact structures with fibrous chromatin than those without cation depletion. Interestingly, the chromatin of EDTA-treated chromosomes reversed to their original granular diameters after re-addition of either Mg2+ or Ca2+ only. These findings signify the importance of divalent cations on the chromosome structure and suggest the interchangeable role of Ca2+ and Mg2+.
16
Gunawardena, S., E. Heddle e M. C. Rykowski. "‘Chromosomal puffing’ in diploid nuclei of Drosophila melanogaster". Journal of Cell Science 108, n. 5 (1 maggio 1995): 1863–72. http://dx.doi.org/10.1242/jcs.108.5.1863.
Testo completoAbstract (sommario):
In situ hybridization has become a powerful technique for dissecting nuclear structure. By localizing nucleic acids with high precision, it is possible to infer the native structure of chromosomes, replication factories and transcript processing complexes. To increase the value of this technique, we have established the limits of resolution of two-color in situ hybridization to chromosomal DNA in diploid chromosomes of Drosophila embryonic nuclei. Using high-resolution 3-dimensional optical microscopy and computational image analysis, we establish that we can distinguish the location of chromosomal sequences that lie 27–29 kb apart within a 40 kb transcription unit with an accuracy of about 100 nm. Contrary to observations made in mammalian tissue culture cells, we find that when the gene is expressed, it assumes an open configuration, and that the extent of decondensation is variable from chromosome to chromosome. Further experiments suggest that variation in gene structure results from asynchrony in transcriptional elongation. We suggest that the phenomenon we observe is the diploid analog to chromosomal puffing that occurs in the transcriptionally active regions of Drosophila polytene chromosomes.
17
Howe, Mary, Kent L. McDonald, Donna G. Albertson e Barbara J. Meyer. "Him-10 Is Required for Kinetochore Structure and Function on Caenorhabditis elegans Holocentric Chromosomes". Journal of Cell Biology 153, n. 6 (11 giugno 2001): 1227–38. http://dx.doi.org/10.1083/jcb.153.6.1227.
Testo completoAbstract (sommario):
Macromolecular structures called kinetochores attach and move chromosomes within the spindle during chromosome segregation. Using electron microscopy, we identified a structure on the holocentric mitotic and meiotic chromosomes of Caenorhabditis elegans that resembles the mammalian kinetochore. This structure faces the poles on mitotic chromosomes but encircles meiotic chromosomes. Worm kinetochores require the evolutionarily conserved HIM-10 protein for their structure and function. HIM-10 localizes to the kinetochores and mediates attachment of chromosomes to the spindle. Depletion of HIM-10 disrupts kinetochore structure, causes a failure of bipolar spindle attachment, and results in chromosome nondisjunction. HIM-10 is related to the Nuf2 kinetochore proteins conserved from yeast to humans. Thus, the extended kinetochores characteristic of C. elegans holocentric chromosomes provide a guide to the structure, molecular architecture, and function of conventional kinetochores.
18
Zakian, V. A., H. M. Blanton, L. Wetzel e G. M. Dani. "Size threshold for Saccharomyces cerevisiae chromosomes: generation of telocentric chromosomes from an unstable minichromosome". Molecular and Cellular Biology 6, n. 3 (marzo 1986): 925–32. http://dx.doi.org/10.1128/mcb.6.3.925-932.1986.
Testo completoAbstract (sommario):
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.
19
Zakian, V. A., H. M. Blanton, L. Wetzel e G. M. Dani. "Size threshold for Saccharomyces cerevisiae chromosomes: generation of telocentric chromosomes from an unstable minichromosome." Molecular and Cellular Biology 6, n. 3 (marzo 1986): 925–32. http://dx.doi.org/10.1128/mcb.6.3.925.
Testo completoAbstract (sommario):
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.
20
Zhao, Jian, Shaobo Jin e Shui Hao. "The substructural organization of the chromosome core (scaffold) in meiotic chromosomes of Trilophidia annulata". Genetical Research 64, n. 3 (dicembre 1994): 209–15. http://dx.doi.org/10.1017/s0016672300032869.
Testo completoAbstract (sommario):
SummaryThe substructural organization of chromosome cores or nonhistone proteins was studied within intact metaphase chromosomes at the second meiotic division in the grasshopper Trilophidia annulata by silver staining as well as light microscopy and whole mount electron microscopy of squash chromosomes. Our results revealed that the metaphase II chromosome contains a longitudinal, helical coiling core structure. Probably the two last organizational levels of the core packaging are achieved by helical coiling. The core structure retains the morphological characteristics of the original metaphase chromosome, surrounded by a halo of dispersed materials, which may be composed mainly of nonhistone proteins. The kinetochore is found to be connected with the chromosome core. The present findings combined with our previous observations on the helical structure of metaphase II chromosomes suggest that the folding path of the internal core structure in metaphase chromosomes is consistent with the final helical arrangement of the chromosome itself. These observations also imply that in condensed metaphase chromosomes nonhistone protein may form a compact network structure with helical appearance, which extends throughout the entire chromosome.
21
Chen, Bo-Wei, Ming-Hsing Lin, Chen-Hsi Chu, Chia-En Hsu e Yuh-Ju Sun. "Insights into ParB spreading from the complex structure of Spo0J and parS". Proceedings of the National Academy of Sciences 112, n. 21 (11 maggio 2015): 6613–18. http://dx.doi.org/10.1073/pnas.1421927112.
Testo completoAbstract (sommario):
Spo0J (stage 0 sporulation protein J, a member of the ParB superfamily) is an essential component of the ParABS (partition system of ParA, ParB, and parS)-related bacterial chromosome segregation system. ParB (partition protein B) and its regulatory protein, ParA, act cooperatively through parS (partition S) DNA to facilitate chromosome segregation. ParB binds to chromosomal DNA at specific parS sites as well as the neighboring nonspecific DNA sites. Various ParB molecules can associate together and spread along the chromosomal DNA. ParB oligomer and parS DNA interact together to form a high-order nucleoprotein that is required for the loading of the structural maintenance of chromosomes proteins onto the chromosome for chromosomal DNA condensation. In this report, we characterized the binding of parS and Spo0J from Helicobacter pylori (HpSpo0J) and solved the crystal structure of the C-terminal domain truncated protein (Ct-HpSpo0J)-parS complex. Ct-HpSpo0J folds into an elongated structure that includes a flexible N-terminal domain for protein–protein interaction and a conserved DNA-binding domain for parS binding. Two Ct-HpSpo0J molecules bind with one parS. Ct-HpSpo0J interacts vertically and horizontally with its neighbors through the N-terminal domain to form an oligomer. These adjacent and transverse interactions are accomplished via a highly conserved arginine patch: RRLR. These interactions might be needed for molecular assembly of a high-order nucleoprotein complex and for ParB spreading. A structural model for ParB spreading and chromosomal DNA condensation that lead to chromosome segregation is proposed.
22
Pizzaia, Daniel, Vanessa M. Oliveira-Maekawa, Aline R. Martins, Mateus Mondin e Margarida L. R. Aguiar-Perecin. "Karyotype structure and NOR activity in Brazilian Smilax Linnaeus, 1753 species (Smilacaceae)". Comparative Cytogenetics 13, n. 3 (22 agosto 2019): 245–63. http://dx.doi.org/10.3897/compcytogen.v13i3.35775.
Testo completoAbstract (sommario):
The genus Smilax Linnaeus, 1753 (Smilacaceae) is a large genus of dioecious plants distributed in tropical, subtropical and temperate regions. Some Smilax species have medicinal importance and their identification is important for the control of raw material used in the manufacture of phytotherapeutical products. The karyotypes of seven Brazilian Smilax species were investigated. Mitotic metaphases of roots from young plants were analysed in Feulgen-stained preparations. The karyotypes were asymmetric and modal with 2n = 2x = 32 chromosomes gradually decreasing in size. In S. goyazana A De Candolle & C De Candolle, 1878, a polyploid species, 2n = 4x = 64. In all the species, the large and medium-sized chromosomes were subtelocentric and submetacentric and the small chromosomes were submetacentric or metacentric. Their karyotypes were quite similar, with differences in the arm ratio of some chromosomes. S. fluminensis Steudel, 1841 differed from the other species by having a large metacentric chromosome 1. These findings suggest that evolution occurred without drastic changes in the chromosomal structure in the species analyzed. Terminal secondary constrictions were visualized on the short arm of some chromosomes, but they were detected only in one homologue of each pair. Due to the terminal location and the degree of chromosome condensation, secondary constrictions were not visualized in some species. The nucleolus organizer regions (NORs) were mapped by silver-staining and fluorescent in situ hybridization (FISH) in S. rufescens Grisebach, 1842 and S. fluminensis. Silver-staining and FISH signals were colocalized on the short arms of six chromosomes in S. rufescens and four chromosomes in S. fluminensis. In FISH preparations, one of the largest chromosomes had the secondary constrictions highly decondensed in some cells. This finding and the heteromorphism observed in Feulgen-stained chromosomes suggest that differential rRNA gene expression between homologous rDNA loci can occur in some cells, resulting in different degrees of ribosomal chromatin decondensation. The presence of a heteromorphic chromosome pair in S. rufescens, S. polyantha Grisebach, 1842 and S. goyazana suggests a chromosomal sex determination in these dioecious species.
23
Sharbel, Timothy F., David M. Green e Andreas Houben. "B-chromosome origin in the endemic New Zealand frog Leiopelma hochstetteri through sex chromosome devolution". Genome 41, n. 1 (1 febbraio 1998): 14–22. http://dx.doi.org/10.1139/g97-091.
Testo completoAbstract (sommario):
The endemic New Zealand frog Leiopelma hochstetteri has variable numbers of mitotically stable B chromosomes. To assess whether the B chromosomes were derived from the autosome complement, they were isolated by micromanipulation and their DNA amplified by degenerate oligonucleotide primed PCR. Southern hybridizations of B chromosome DNA probes to genomic DNA from males and females characterized by differing numbers of B chromosomes demonstrated that the B chromosomes were derived from the univalent W sex chromosome characteristic of North Island populations. The presence of homologous B chromosome specific sequences from geographically distinct populations indicates a single origin of the B chromosomes. Furthermore, a primitive homology shared by B chromosomes and the W sex chromosome from an ancestral WZ/ZZ karyotype, which is still present in frogs from Great Barrier Island, shows that the B chromosomes originated soon after the univalent W sex chromosome had originated. Sequence analysis revealed that B chromosome DNA is composed of repeat sequences and has the potential to form stable hairpin structures. The molecular dynamics of these structures may reflect an inherent propensity to undergo rapid change in nucleotide sequence and chromosome structure.
24
Sajid, Atiqa, El-Nasir Lalani, Bo Chen, Teruo Hashimoto, Darren K. Griffin, Archana Bhartiya, George Thompson, Ian K. Robinson e Mohammed Yusuf. "Ultra-Structural Imaging Provides 3D Organization of 46 Chromosomes of a Human Lymphocyte Prophase Nucleus". International Journal of Molecular Sciences 22, n. 11 (1 giugno 2021): 5987. http://dx.doi.org/10.3390/ijms22115987.
Testo completoAbstract (sommario):
Three dimensional (3D) ultra-structural imaging is an important tool for unraveling the organizational structure of individual chromosomes at various stages of the cell cycle. Performing hitherto uninvestigated ultra-structural analysis of the human genome at prophase, we used serial block-face scanning electron microscopy (SBFSEM) to understand chromosomal architectural organization within 3D nuclear space. Acquired images allowed us to segment, reconstruct, and extract quantitative 3D structural information about the prophase nucleus and the preserved, intact individual chromosomes within it. Our data demonstrate that each chromosome can be identified with its homolog and classified into respective cytogenetic groups. Thereby, we present the first 3D karyotype built from the compact axial structure seen on the core of all prophase chromosomes. The chromosomes display parallel-aligned sister chromatids with familiar chromosome morphologies with no crossovers. Furthermore, the spatial positions of all 46 chromosomes revealed a pattern showing a gene density-based correlation and a neighborhood map of individual chromosomes based on their relative spatial positioning. A comprehensive picture of 3D chromosomal organization at the nanometer level in a single human lymphocyte cell is presented.
25
Liu, Wan-Sheng. "Mammalian Sex Chromosome Structure, Gene Content, and Function in Male Fertility". Annual Review of Animal Biosciences 7, n. 1 (15 febbraio 2019): 103–24. http://dx.doi.org/10.1146/annurev-animal-020518-115332.
Testo completoAbstract (sommario):
Mammalian sex chromosomes evolved from an ordinary pair of autosomes. The X chromosome is highly conserved, whereas the Y chromosome varies among species in size, structure, and gene content. Unlike autosomes that contain randomly mixed collections of genes, the sex chromosomes are enriched in testis-biased genes related to sexual development and reproduction, particularly in spermatogenesis and male fertility. This review focuses on how sex chromosome dosage compensation takes place and why meiotic sex chromosome inactivation occurs during spermatogenesis. Furthermore, the review also emphasizes how testis-biased genes are enriched on the sex chromosomes and their functions in male fertility. It is concluded that sex chromosomes are critical to sexual development and male fertility; however, our understanding of how sex chromosome genes direct sexual development and fertility has been hampered by the structural complexities of the sex chromosomes and by the multicopy nature of the testis gene families that also play a role in immunity, cancer development, and brain function.
26
Li, Ziang, Yunfei Bi, Xing Wang, Yunzhu Wang, Shuqiong Yang, Zhentao Zhang, Jinfeng Chen e Qunfeng Lou. "Chromosome identification in Cucumis anguria revealed by cross-species single-copy gene FISH". Genome 61, n. 6 (giugno 2018): 397–404. http://dx.doi.org/10.1139/gen-2017-0235.
Testo completoAbstract (sommario):
Cucumis anguria is a potential genetic resource for improving crops of the genus Cucumis, owing to its broad-spectrum resistance. However, few cytogenetic studies on C. anguria have been reported because of its small metaphase chromosomes and the scarcity of distinguished chromosomal landmarks. In this study, 14 single-copy genes from cucumber and rDNAs were used as probes for FISH to identify the individual chromosomes of C. anguria. The distinctive signal distribution patterns of the probes allowed us to distinguish each chromosome of C. anguria (A01–A12). Further, detailed chromosome characteristics were obtained through pachytene chromosome FISH. The lengths of pachytene chromosomes varied from 54.80 to 143.41 μm. The proportion of heterochromatin regions varied from 13.56% to 63.86%. Finally, the chromosomal homeologous relationship between C. anguria and cucumber (C1–C7) was analyzed. The results showed that A06 + A09, A03 + A12, A02 + A04, and A01 + A11 were homeologs of C1, C2, C3, and C6, respectively. Furthemore, chromosomes A08, A10, and A05 were homeologs of C4, C5, and C7, respectively. Chromosome identification and homeologous relationship analysis between C. anguria and cucumber lay the foundation for further research of genome structure evolution in species of Cucumis.
27
Brinkley, B. R., e R. P. Zinkowski. "Scleroderma crest autoantibodies as fluorescent and Immuno-Electron Microscopic probes: Keys to a chromosomal black box". Proceedings, annual meeting, Electron Microscopy Society of America 49 (agosto 1991): 12–13. http://dx.doi.org/10.1017/s0424820100084363.
Testo completoAbstract (sommario):
The mammalian kinetochore is a highly differentiated structure found at the centromere (primary constriction) of chromosomes that serves as an attachment site for spindle microtubules. Ultrastructurally, the kinetochore typically appears as a tri-layered plate or disc situated at the sides of the centromere (Fig.1). Recent evidence demonstrates that kinetochores have the ability to capture and stabilize microtubules that grow from the spindle poles. Moreover, the motor(s) for chromosome movement appear to be located in or near the kinetochore which actively participates in the generation of forces necessary for chromosome movement in mitosis and meiosis. To understand how the precise ballet-like movements of chromosomes on the mitotic spindle occur, attention has focused on the “black box” of the chromosome; the centromere-kinetochore complex.The fortuitous discovery that serum from individuals with the CREST variant of scleroderma contain autoantibodies that bind to components of the centromere-kinetochore complex has led to major advancements in the understanding of this chromosomal black box. Indirect immunofluorescence has demonstrated the presence of paired fluorescent structures (Fig.2) at the centromeres of both mammalian and plant chromosomes.
28
Wang, Xu-Ting, e Bin-Guang Ma. "Spatial Chromosome Organization and Adaptation of Escherichia coli under Heat Stress". Microorganisms 12, n. 6 (19 giugno 2024): 1229. http://dx.doi.org/10.3390/microorganisms12061229.
Testo completoAbstract (sommario):
The spatial organization of bacterial chromosomes is crucial for cellular functions. It remains unclear how bacterial chromosomes adapt to high-temperature stress. This study delves into the 3D genome architecture and transcriptomic responses of Escherichia coli under heat-stress conditions to unravel the intricate interplay between the chromosome structure and environmental cues. By examining the role of macrodomains, chromosome interaction domains (CIDs), and nucleoid-associated proteins (NAPs), this work unveils the dynamic changes in chromosome conformation and gene expression patterns induced by high-temperature stress. It was observed that, under heat stress, the short-range interaction frequency of the chromosomes decreased, while the long-range interaction frequency of the Ter macrodomain increased. Furthermore, two metrics, namely, Global Compactness (GC) and Local Compactness (LC), were devised to measure and compare the compactness of the chromosomes based on their 3D structure models. The findings in this work shed light on the molecular mechanisms underlying thermal adaptation and chromosomal organization in bacterial cells, offering valuable insights into the complex inter-relationships between environmental stimuli and genomic responses.
29
Strehl, S., J. M. LaSalle e M. Lalande. "High-resolution analysis of DNA replication domain organization across an R/G-band boundary." Molecular and Cellular Biology 17, n. 10 (ottobre 1997): 6157–66. http://dx.doi.org/10.1128/mcb.17.10.6157.
Testo completoAbstract (sommario):
Establishing how mammalian chromosome replication is regulated and how groups of replication origins are organized into replication bands will significantly increase our understanding of chromosome organization. Replication time bands in mammalian chromosomes show overall congruency with structural R- and G-banding patterns as revealed by different chromosome banding techniques. Thus, chromosome bands reflect variations in the longitudinal structure and function of the chromosome, but little is known about the structural basis of the metaphase chromosome banding pattern. At the microscopic level, both structural R and G bands and replication bands occupy discrete domains along chromosomes, suggesting separation by distinct boundaries. The purpose of this study was to determine replication timing differences encompassing a boundary between differentially replicating chromosomal bands. Using competitive PCR on replicated DNA from flow-sorted cell cycle fractions, we have analyzed the replication timing of markers spanning roughly 5 Mb of human chromosome 13q14.3/q21.1. This is only the second report of high-resolution analysis of replication timing differences across an R/G-band boundary. In contrast to previous work, however, we find that band boundaries are defined by a gradient in replication timing rather than by a sharp boundary separating R and G bands into functionally distinct chromatin compartments. These findings indicate that topographical band boundaries are not defined by specific sequences or structures.
30
Roslan, Nurzanariah, Karmila Kamil e Chong Kok Hen. "Double Helix Structure and Finite Persisting Sphere Genetic Algorithm in Designing Digital Circuit Structure". International Journal for Innovation Education and Research 2, n. 3 (31 marzo 2014): 92–107. http://dx.doi.org/10.31686/ijier.vol2.iss3.158.
Testo completoAbstract (sommario):
This paper proposes a new approach of chromosome representation in digital circuit design which is Double Helix Structure (DHS). The idea of DHS in chromosome representation is inspired from the nature of the DNA's structure that built up the formation of the chromosomes. DHS is an uncomplicated design method. It uses short chromosome string to represent the circuit structure. This new structure representation is flexible in size where it is not restricted by the conventional matrix structure representation. There are some advantages of the proposed method such as convenience to apply due to the simple formation and flexible structure, less requirement of memory allocation and faster processing time due to the short chromosomes representation. In this paper, DHS is combined with Finite Persisting Sphere Genetic Algorithm (FPSGA) to optimal the digital circuit structure design. The experimental results prove that DHS uses short chromosome string to produce the flexible digital circuit structure and FPSGA further optimal the number of gates used in the structure. The proposed method has better performance compared to other methods.
31
Marec, František, e Walther Traut. "Sex chromosome pairing and sex chromatin bodies in W–Z translocation strains of Ephestia kuehniella (Lepidoptera)". Genome 37, n. 3 (1 giugno 1994): 426–35. http://dx.doi.org/10.1139/g94-060.
Testo completoAbstract (sommario):
Structure and pairing behavior of sex chromosomes in females of four T(W;Z) lines of the Mediterranean flour moth, Ephestia kuehniella, were investigated using light and electron microscopic techniques and compared with the wild type. In light microscopic preparations of pachytene oocytes of wild-type females, the WZ bivalent stands out by its heterochromatic W chromosome strand. In T(W;Z) females, the part of the Z chromosome that was translated onto the W chromosome was demonstrated as a distal segment of the neo-W chromosome, displaying a characteristic non-W chromosomal chromomere–interchromomere pattern. This segment is homologously paired with the corresponding part of a complete Z chromosome. In contrast with the single ball of heterochromatic W chromatin in highly polyploid somatic nuclei of wild-type females, the translocation causes the formation of deformed or fragmented W chromatin bodies, probably owing to opposing tendencies of the Z and W chromosomal parts of the neo-W. In electron microscopic preparations of microspread nuclei, sex chromosome bivalents were identified by the remnants of electron-dense heterochromatin tangles decorating the W chromosome axis, by the different lengths of the Z and W chromosome axes, and by incomplete pairing. No heterochromatin tangles were attached to the translocated segment of the Z chromosome at one end of the neo-W chromosome. Because of the homologous pairing between the translocation and the structurally normal Z chromosome, pairing affinity of sex chromosomes in T(W;Z) females is significantly improved. Specific differences observed among T(W;Z)1–4 translocations are probably due to the different lengths of the translocated segments.Key words: Mediterranean flour moth, sex chromosomes, sex chromatin, translocations, synaptonemal complexes, microspreading.
32
Silva, Maelin, Duílio Mazzoni Zerbinato Andrade Silva, Jonathan Pena Castro, Alex I. Makunin, Felipe Faix Barby, Edivaldo Herculano Correa de Oliveira, Thomas Liehr et al. "Investigation of Astyanax mexicanus (Characiformes, Characidae) chromosome 1 structure reveals unmapped sequences and suggests conserved evolution". PLOS ONE 19, n. 11 (18 novembre 2024): e0313896. http://dx.doi.org/10.1371/journal.pone.0313896.
Testo completoAbstract (sommario):
Natural selection in the cave habitat has resulted in unique phenotypic traits (including pigmentation loss and ocular degeneration) in the Mexican tetra Astyanax mexicanus, considered a model species for evolutionary research. A. mexicanus has a karyotype of 2n = 50 chromosomes, and long-read sequencing and quantitative trait linkage maps (QTLs) have completely reconstructed the reference genome at the chromosomal level. In the current work, we performed whole chromosome isolation by microdissection and total amplification using DOP-PCR and Whole Chromosome Painting (WCP), followed by sequencing on the Illumina NextSeq platform, to investigate the microstructure of the large and conserved metacentric chromosome 1 of A. mexicanus. The sequences aligned to linkage block 3 of the reference genome, as determined by processing the reads with the DOPseq pipeline and characterizing the satellites with the TAREAN program. In addition, part of the sequences was anchored in linkage blocks that have not yet been assigned to the chromosomes. Furthermore, fluorescence in situ hybridization using WCP 1 carried out in other nearby species revealed a high degree of chromosome conservation, which allows us to hypothesize a common origin of this element. The physical mapping of the repetitive marker sequences provided a micro- and macrostructural overview and confirmed their position in chromosome pair 1. These sequences can serve as comparative tools for understanding the evolution and organization of this chromosome in other species of the family in future studies.
33
Strukov, Yuri G., Yan Wang e Andrew S. Belmont. "Engineered chromosome regions with altered sequence composition demonstrate hierarchical large-scale folding within metaphase chromosomes". Journal of Cell Biology 162, n. 1 (30 giugno 2003): 23–35. http://dx.doi.org/10.1083/jcb.200303098.
Testo completoAbstract (sommario):
Mitotic chromosome structure and DNA sequence requirements for normal chromosomal condensation remain unknown. We engineered labeled chromosome regions with altered scaffold-associated region (SAR) sequence composition as a formal test of the radial loop and other chromosome models. Chinese hamster ovary cells were isolated containing high density insertions of a transgene containing lac operator repeats and a dihydrofolate reductase gene, with or without flanking SAR sequences. Lac repressor staining provided high resolution labeling with good preservation of chromosome ultrastructure. No evidence emerged for differential targeting of SAR sequences to a chromosome axis within native chromosomes. SAR sequences distributed uniformly throughout the native chromosome cross section and chromosome regions containing a high density of SAR transgene insertions showed normal diameter and folding. Ultrastructural analysis of two different transgene insertion sites, both spanning less than the full chromatin width, clearly contradicted predictions of simple radial loop models while providing strong support for hierarchical models of chromosome architecture. Specifically, an ∼250-nm-diam folding subunit was visualized directly within fully condensed metaphase chromosomes. Our results contradict predictions of simple radial loop models and provide the first unambiguous demonstration of a hierarchical folding subunit above the level of the 30-nm fiber within normally condensed metaphase chromosomes.
34
Liang, Jiangtao, Simon M. Bondarenko, Igor V. Sharakhov e Maria V. Sharakhova. "Visualization of the Linear and Spatial Organization of Chromosomes in Mosquitoes". Cold Spring Harbor Protocols 2022, n. 12 (5 agosto 2022): pdb.top107732. http://dx.doi.org/10.1101/pdb.top107732.
Testo completoAbstract (sommario):
Mosquitoes are vectors of dangerous human diseases such as malaria, dengue, Zika, West Nile fever, and lymphatic filariasis. Visualization of the linear and spatial organization of mosquito chromosomes is important for understanding genome structure and function. Utilization of chromosomal inversions as markers for population genetics studies yields insights into mosquito adaptation and evolution. Cytogenetic approaches assist with the development of chromosome-scale genome assemblies that are useful tools for studying mosquito biology and for designing novel vector control strategies. Fluorescence in situ hybridization is a powerful technique for localizing specific DNA sequences within the linear chromosome structure and within the spatial organization of the cell nucleus. Here, we introduce protocols used in our laboratories for chromosome visualization and their application in mosquitoes.
35
Al-Ardi, Musafer. "Illumination on the structure and characteristics of Entamoeba histolytica genome." Al-Qadisiyah Journal Of Pure Science 26, n. 4 (5 luglio 2021): 19–26. http://dx.doi.org/10.29350/qjps.2021.26.4.1311.
Testo completoAbstract (sommario):
Entamoeba histolytica, likes other Organismes, is characterized by diversity and heterogeneity in its genetic content, which is one of the most paramount reasons for survival, and the increase in susceptibility to infection. Non-condensation of chromosomes during the process of cell division and the ambiguity of the chromosomal ploidy makes predicting the exact chromosomal numeral difficult. Genes distributed across 14 chromosomes as well as many extra-chromosome elements. Most Genes compose of one axon only, with Introns in 25% of Genes. This genome is characterized by the presence of Polymorphic internal repeat regions, and several gene families, one of these large families encoding Transmembrane kinas, Cysteine protease (CP), SREHP protein, and others.
36
Heldrich, Jonna, Xiaoji Sun, Luis A. Vale-Silva, Tovah E. Markowitz e Andreas Hochwagen. "Topoisomerases Modulate the Timing of Meiotic DNA Breakage and Chromosome Morphogenesis in Saccharomyces cerevisiae". Genetics 215, n. 1 (9 marzo 2020): 59–73. http://dx.doi.org/10.1534/genetics.120.303060.
Testo completoAbstract (sommario):
During meiotic prophase, concurrent transcription, recombination, and chromosome synapsis place substantial topological strain on chromosomal DNA, but the role of topoisomerases in this context remains poorly defined. Here, we analyzed the roles of topoisomerases I and II (Top1 and Top2) during meiotic prophase in Saccharomyces cerevisiae. We show that both topoisomerases accumulate primarily in promoter-containing intergenic regions of actively transcribing genes, including many meiotic double-strand break (DSB) hotspots. Despite the comparable binding patterns, top1 and top2 mutations have different effects on meiotic recombination. TOP1 disruption delays DSB induction and shortens the window of DSB accumulation by an unknown mechanism. By contrast, temperature-sensitive top2-1 mutants exhibit a marked delay in meiotic chromosome remodeling and elevated DSB signals on synapsed chromosomes. The problems in chromosome remodeling were linked to altered Top2 binding patterns rather than a loss of Top2 catalytic activity, and stemmed from a defect in recruiting the chromosome remodeler Pch2/TRIP13 to synapsed chromosomes. No chromosomal defects were observed in the absence of TOP1. Our results imply independent roles for Top1 and Top2 in modulating meiotic chromosome structure and recombination.
37
Jackson, S. A., J. Jiang, B. Friebe e B. S. Gill. "Structure of the rye midget chromosome analyzed by FISH and C-banding". Genome 40, n. 5 (1 ottobre 1997): 782–84. http://dx.doi.org/10.1139/g97-801.
Testo completoAbstract (sommario):
The diminutive "midget" chromosome derived from rye (Secale cereale) was analyzed by C-banding and fluorescence in situ hybridization (FISH) using DNA probe pSau3A9 that is located in the centromeres of cereal chromosomes. FISH signals were detected at one end and overlapped one of the two telomeres of the midget, indicating that the midget is a telocentric chromosome. The FISH and C-banding results show that the centromere of the midget chromosome is smaller than those of normal wheat and rye chromosomes. These results indicate that one of the breakpoints occurred in the middle of the centromere of rye chromosome 1R during generation of the midget.Key words: Secale cereale, midget chromosome, centromere, telomere
38
Romanenko, Svetlana A., Antonina V. Smorkatcheva, Yulia M. Kovalskaya, Dmitry Yu Prokopov, Natalya A. Lemskaya, Olga L. Gladkikh, Ivan A. Polikarpov et al. "Complex Structure of Lasiopodomys mandarinus vinogradovi Sex Chromosomes, Sex Determination, and Intraspecific Autosomal Polymorphism". Genes 11, n. 4 (30 marzo 2020): 374. http://dx.doi.org/10.3390/genes11040374.
Testo completoAbstract (sommario):
The mandarin vole, Lasiopodomys mandarinus, is one of the most intriguing species among mammals with non-XX/XY sex chromosome system. It combines polymorphism in diploid chromosome numbers, variation in the morphology of autosomes, heteromorphism of X chromosomes, and several sex chromosome systems the origin of which remains unexplained. Here we elucidate the sex determination system in Lasiopodomys mandarinus vinogradovi using extensive karyotyping, crossbreeding experiments, molecular cytogenetic methods, and single chromosome DNA sequencing. Among 205 karyotyped voles, one male and three female combinations of sex chromosomes were revealed. The chromosome segregation pattern and karyomorph-related reproductive performances suggested an aberrant sex determination with almost half of the females carrying neo-X/neo-Y combination. The comparative chromosome painting strongly supported this proposition and revealed the mandarin vole sex chromosome systems originated due to at least two de novo autosomal translocations onto the ancestral X chromosome. The polymorphism in autosome 2 was not related to sex chromosome variability and was proved to result from pericentric inversions. Sequencing of microdissection derived of sex chromosomes allowed the determination of the coordinates for syntenic regions but did not reveal any Y-specific sequences. Several possible sex determination mechanisms as well as interpopulation karyological differences are discussed.
39
Meng, Zhuang, Xiaoxu Hu, Zhiliang Zhang, Zhanjie Li, Qingfang Lin, Mei Yang, Pingfang Yang, Ray Ming, Qingyi Yu e Kai Wang. "Chromosome Nomenclature and Cytological Characterization of Sacred Lotus". Cytogenetic and Genome Research 153, n. 4 (2017): 223–31. http://dx.doi.org/10.1159/000486777.
Testo completoAbstract (sommario):
Sacred lotus is a basal eudicot plant that has been cultivated in Asia for over 7,000 years for its agricultural, ornamental, religious, and medicinal importance. A notable characteristic of lotus is the seed longevity. Extensive endeavors have been devoted to dissect its genome assembly, including the variety China Antique, which germinated from a 1,300-year-old seed. Here, cytogenetic markers representing the 10 largest megascaffolds, which constitute approximately 70% of the lotus genome assembly, were developed. These 10 megascaffolds were then anchored to the corresponding lotus chromosomes by fluorescence in situ hybridization using these cytogenetic markers, and a set of chromosome-specific cytogenetic markers that could unambiguously identify each of the 8 chromosomes was generated. Karyotyping was conducted, and a nomenclature based on chromosomal length was established for the 8 chromosomes of China Antique. Comparative karyotyping revealed relatively conserved chromosomal structures between China Antique and 3 modern cultivars. Interestingly, significant variations in the copy number of 45S rDNA were detected between China Antique and modern cultivars. Our results provide a comprehensive view on the chromosomal structure of sacred lotus and will facilitate further studies and the genome assembly of lotus.
40
Houchmandzadeh, Bahram, e Stefan Dimitrov. "Elasticity Measurements Show the Existence of Thin Rigid Cores Inside Mitotic Chromosomes". Journal of Cell Biology 145, n. 2 (19 aprile 1999): 215–23. http://dx.doi.org/10.1083/jcb.145.2.215.
Testo completoAbstract (sommario):
Chromosome condensation is one of the most critical steps during cell division. However, the structure of condensed mitotic chromosomes is poorly understood. In this paper we describe a new approach based on elasticity measurements for studying the structure of in vitro assembled mitotic chromosomes in Xenopus egg extract. The approach is based on a unique combination of measurements of both longitudinal deformability and bending rigidity of whole chromosomes. By using specially designed micropipettes, the chromosome force–extension curve was determined. Analysis of the curvature fluctuation spectrum allowed for the measurement of chromosome bending ridigity. The relationship between the values of these two parameters is very specific: the measured chromosome flexibility was found to be 2,000 times lower than the flexibility calculated from the experimentally determined Young modulus. This requires the chromosome structure to be formed of one or a few thin rigid elastic axes surrounded by a soft envelope. The properties of these axes are well-described by models developed for the elasticity of titin-like molecules. Additionally, the deformability of in vitro assembled chromosomes was found to be very similar to that of native somatic chromosomes, thus demonstrating the existence of an essentially identical structure.
41
Atli, Emine Ikbal, Hakan Gurkan, Engin Atli, Ulfet Vatansever, Betul Acunas e Cisem Mail. "De Novo Subtelomeric 6p25.3 Deletion with Duplication of 6q23.3-q27: Genotype–Phenotype Correlation". Journal of Pediatric Genetics 09, n. 01 (12 agosto 2019): 032–39. http://dx.doi.org/10.1055/s-0039-1694703.
Testo completoAbstract (sommario):
AbstractDuplications of 6q and deletions of 6p have been reported in more than 30 cases of live born infants and given rise to widespread abnormalities recognizable as a specific clinical syndrome. Different phenotypes have been described with variable clinical signs. Most cases involve the coexistence of unbalanced translocations affecting one or the other of the chromosomes. However, duplication of both chromosome 6q and deletion of 6p regions have been reported in only a few cases. Here, we report the first duplication of chromosome band 6q23.3–q27 with deletion of 6p25.3. This is the first case in the literature involving changes to these specific chromosomal regions; a medium size duplication of the distal long arm and smaller deletion of the terminal short arm of chromosome 6. In the literature, there are no other cases where these two specific chromosomal aberrations are observed together. Conventional chromosome analysis was performed to investigate the patient. Chromosome structure was identified using fluorescence in situ hybridization for subtelomeric regions of chromosome 6 and array comparative genomic hybridization analysis (array-CGH).
42
Shopland, Lindsay S., Christopher R. Lynch, Kevin A. Peterson, Kathleen Thornton, Nick Kepper, Johann von Hase, Stefan Stein et al. "Folding and organization of a contiguous chromosome region according to the gene distribution pattern in primary genomic sequence". Journal of Cell Biology 174, n. 1 (3 luglio 2006): 27–38. http://dx.doi.org/10.1083/jcb.200603083.
Testo completoAbstract (sommario):
Specific mammalian genes functionally and dynamically associate together within the nucleus. Yet, how an array of many genes along the chromosome sequence can be spatially organized and folded together is unknown. We investigated the 3D structure of a well-annotated, highly conserved 4.3-Mb region on mouse chromosome 14 that contains four clusters of genes separated by gene “deserts.” In nuclei, this region forms multiple, nonrandom “higher order” structures. These structures are based on the gene distribution pattern in primary sequence and are marked by preferential associations among multiple gene clusters. Associating gene clusters represent expressed chromatin, but their aggregation is not simply dependent on ongoing transcription. In chromosomes with aggregated gene clusters, gene deserts preferentially align with the nuclear periphery, providing evidence for chromosomal region architecture by specific associations with functional nuclear domains. Together, these data suggest dynamic, probabilistic 3D folding states for a contiguous megabase-scale chromosomal region, supporting the diverse activities of multiple genes and their conserved primary sequence organization.
43
Sarvetnick, Nora, Howard S. Fox, Elizabeth Mann, Paul E. Mains, Rosemary W. Elliott e Lee M. Silver. "NONHOMOLOGOUS PAIRING IN MICE HETEROZYGOUS FOR A t HAPLOTYPE CAN PRODUCE RECOMBINANT CHROMOSOMES WITH DUPLICATIONS AND DELETIONS". Genetics 113, n. 3 (1 luglio 1986): 723–34. http://dx.doi.org/10.1093/genetics/113.3.723.
Testo completoAbstract (sommario):
ABSTRACT We have investigated the structure and properties of a chromosomal product recovered from a rare recombination event between a t haplotype and a wild-type form of mouse chromosome 17. Our embryological and molecular studies indicate that this chromosome (twLub 2) is characterized by both a deletion and duplication of adjacent genetic material. The deletion appears to be responsible for a dominant lethal maternal effect and a recessive embryonic lethality. The duplication provides an explanation for the twLub 2 suppression of the dominant T locus phenotype. A reanalysis of previously described results with another chromosome 17 variant called TtOrl indicates a structure for this chromosome that is reciprocal to that observed for twLub 2. We have postulated the existence of an inversion over the proximal portion of all complete t haplotypes in order to explain the generation of the partial t haplotypes twLub 2 and TtOrl. This proximal inversion and the previously described distal inversion are sufficient to account for all of the recombination properties that are characteristic of complete t haplotypes. The structures determined for twLub 2 and TtOrl indicate that rare recombination can occur between nonequivalent genomic sequences within the inverted proximal t region when wild-type and t chromosomes are paired in a linear, nonhomologous configuration.
44
Krylov, Vladimir, T. Tlapáková, J. Mácha, J. Curlej, L. Ryban e P. Chrenek. "Localization of Human Coagulation Factor VIII (hFVIII) in Transgenic Rabbit by FISH-TSA: Identification of Transgene Copy Number and Transmission to the Next Generation". Folia Biologica 54, n. 4 (2008): 121–24. http://dx.doi.org/10.14712/fb2008054040121.
Testo completoAbstract (sommario):
For chromosomal localization of the hFVIII human transgene in F2 and F3 generation of transgenic rabbits, FISH-TSA was applied. A short cDNA probe (1250 bp) targeted chromosomes 3, 7, 8, 9 and 18 of an F2 male (animal 1-3-8). Two transgenic off-spring (F3) revealed signal positions in chromosome 3 and chromosomes 3 and 7, respectively. Sequencing and structure analysis of the rabbit orthologous gene revealed high similarity to its human counterpart. Part of the sequenced cDNA (1310 bp) served as a probe for FISH-TSA analysis. The rabbit gene was localized in the q arm terminus of the X chromosome. This result is in agreement with reciprocal chromosome painting between the rabbit and the human. The presented FISH-TSA method provides strong signals without any interspecies reactivity.
45
Vieira, Cristina P., Paula A. Coelho e Jorge Vieira. "Inferences on the Evolutionary History of theDrosophila americanaPolymorphicX/4Fusion From Patterns of Polymorphism at theX-LinkedparalyticandelavGenes". Genetics 164, n. 4 (1 agosto 2003): 1459–69. http://dx.doi.org/10.1093/genetics/164.4.1459.
Testo completoAbstract (sommario):
AbstractIn Drosophila there is limited evidence on the nature of evolutionary forces affecting chromosomal arrangements other than inversions. The study of the X/4 fusion polymorphism of Drosophila americana is thus of interest. Polymorphism patterns at the paralytic (para) gene, located at the base of the X chromosome, suggest that there is suppressed crossing over in this region between fusion and nonfusion chromosomes but not within fusion and nonfusion chromosomes. These data are thus compatible with previous claims that within fusion chromosomes the amino acid clines found at fused1 (also located at the base of the X chromosome) are likely maintained by local selection. The para data set also suggests a young age of the X/4 fusion. Polymorphism data on para and elav (located at the middle region of the X chromosome) suggest that there is no population structure other than that caused by the X/4 fusion itself. These findings are therefore compatible with previous claims that selection maintains the strong association observed between the methionine/threonine variants at fused1 and the status of the X chromosome as fused or unfused to the fourth chromosome.
46
Bazaz, Asim Iqbal, Irfan Ahmad, Tasaduq H. Shah e Nafath-ul-Arab Arab. "Karyomorphometric analysis of fresh water fish species of India, with special reference to cold water fishes of Kashmir Himalayas. A Mini Review". Caryologia 75, n. 1 (7 luglio 2022): 109–21. http://dx.doi.org/10.36253/caryologia-1362.
Testo completoAbstract (sommario):
Cytogenetics is the diagnostic study of chromosomal structure and properties, as well as cell division, using a variety of methods, one of which is “karyotyping.” It refers to a method of photographing a stained preparation in which the chromosomes are organised in a uniform pattern. The advent of modern techniques such as “karyotyping” has made it feasible to visualize undetected chromosomal abnormalities such as short chromosome segments and chromosome translocations. Because such techniques enabled each pair of chromosomes to be identified separately, they have further aided our understanding of the chromosomal basis of a certain significant genetic diseases. Every organism has its own unique karyotype, which is defined by its number and shape. Karyotypic variation, on the other hand, occurs in different individuals of the same species, as well as between different species. Monitoring cytogenetic data of economically significant fishes as well as threatened fishes can hold importance of the succeeding generations. This review article highlights the variation in the chromosomal number & classification, methods of chromosome preparation and karyotypic analysis of various fish species of India with a special reference to fishes of Kashmir Himalayas.
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Glass, J. R., e L. Gerace. "Lamins A and C bind and assemble at the surface of mitotic chromosomes." Journal of Cell Biology 111, n. 3 (1 settembre 1990): 1047–57. http://dx.doi.org/10.1083/jcb.111.3.1047.
Testo completoAbstract (sommario):
To study a possible interaction of nuclear lamins with chromatin, we examined assembly of lamins A and C at mitotic chromosome surfaces in vitro. When a postmicrosomal supernatant of metaphase CHO cells containing disassembled lamins A and C is incubated with chromosomes isolated from mitotic Chinese hamster ovary cells, lamins A and C undergo dephosphorylation and uniformly coat the chromosome surfaces. Furthermore, when purified rat liver lamins A and C are dialyzed with mitotic chromosomes into a buffer of physiological ionic strength and pH, lamins A and C coat chromosomes in a similar fashion. In both cases a lamin-containing supramolecular structure is formed that remains intact when the chromatin is removed by digestion with micrococcal nuclease and extraction with 0.5 M KCl. Lamins associate with chromosomes at concentrations approximately eightfold lower than the critical concentration at which they self-assemble into insoluble structures in the absence of chromosomes, indicating that chromosome surfaces contain binding sites that promote lamin assembly. These binding sites are destroyed by brief treatment of chromosomes with trypsin or micrococcal nuclease. Together, these data suggest the existence of a specific lamin-chromatin interaction in cells that may be important for nuclear envelope reassembly and interphase chromosome structure.
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Nielsen, Christian F., Tao Zhang, Marin Barisic, Paul Kalitsis e Damien F. Hudson. "Topoisomerase IIα is essential for maintenance of mitotic chromosome structure". Proceedings of the National Academy of Sciences 117, n. 22 (15 maggio 2020): 12131–42. http://dx.doi.org/10.1073/pnas.2001760117.
Testo completoAbstract (sommario):
Topoisomerase IIα (TOP2A) is a core component of mitotic chromosomes and important for establishing mitotic chromosome condensation. The primary roles of TOP2A in mitosis have been difficult to decipher due to its multiple functions across the cell cycle. To more precisely understand the role of TOP2A in mitosis, we used the auxin-inducible degron (AID) system to rapidly degrade the protein at different stages of the human cell cycle. Removal of TOP2A prior to mitosis does not affect prophase timing or the initiation of chromosome condensation. Instead, it prevents chromatin condensation in prometaphase, extends the length of prometaphase, and ultimately causes cells to exit mitosis without chromosome segregation occurring. Surprisingly, we find that removal of TOP2A from cells arrested in prometaphase or metaphase cause dramatic loss of compacted mitotic chromosome structure and conclude that TOP2A is crucial for maintenance of mitotic chromosomes. Treatments with drugs used to poison/inhibit TOP2A function, such as etoposide and ICRF-193, do not phenocopy the effects on chromosome structure of TOP2A degradation by AID. Our data point to a role for TOP2A as a structural chromosome maintenance enzyme locking in condensation states once sufficient compaction is achieved.
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Hamano, Tohru, Astari Dwiranti, Kohei Kaneyoshi, Shota Fukuda, Reo Kometani, Masayuki Nakao, Hideaki Takata, Susumu Uchiyama, Nobuko Ohmido e Kiichi Fukui. "Chromosome Interior Observation by Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) Using Ionic Liquid Technique". Microscopy and Microanalysis 20, n. 5 (10 luglio 2014): 1340–47. http://dx.doi.org/10.1017/s143192761401280x.
Testo completoAbstract (sommario):
AbstractAttempts to elucidate chromosome structure have long remained elusive. Electron microscopy is useful for chromosome structure research because of its high resolution and magnification. However, biological samples such as chromosomes need to be subjected to various preparation steps, including dehydration, drying, and metal/carbon coating, which may induce shrinkage and artifacts. The ionic liquid technique has recently been developed and it enables sample preparation without dehydration, drying, or coating, providing a sample that is closer to the native condition. Concurrently, focused ion beam/scanning electron microscopy (FIB/SEM) has been developed, allowing the investigation and direct analysis of chromosome interiors. In this study, we investigated chromosome interiors by FIB/SEM using plant and human chromosomes prepared by the ionic liquid technique. As a result, two types of chromosomes, with and without cavities, were visualized, both for barley and human chromosomes prepared by critical point drying. However, chromosome interiors were revealed only as a solid structure, lacking cavities, when prepared by the ionic liquid technique. Our results suggest that the existence and size of cavities depend on the preparation procedures. We conclude that combination of the ionic liquid technique and FIB/SEM is a powerful tool for chromosome study.
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McMaster, Terence J., Mervyn J. Miles, Mark O. Winfield e Angela Karp. "Analysis off cereal chromosomes by atomic force microscopy". Genome 39, n. 2 (1 aprile 1996): 439–44. http://dx.doi.org/10.1139/g96-055.
Testo completoAbstract (sommario):
Atomic force microscopy has been applied to the study of plant chromosomes from cereal grasses Triticum aestivum (bread wheat), Triticum tauschii, and Hordeum vulgare (barley). Using standard mitotic metaphase squashes, high resolution images have been obtained of untreated chromosomes and also of chromosomes after C-banding, N-banding, and in situ hybridization. The true 3-dimensional nature of the images permits detailed analysis of the surface structure and, on untreated uncoated chromosomes, surface features on a length scale consistent with nucleosome structures have been observed. C+ and N+ regions are manifest as areas of high relief on a slightly collapsed chromosome structure. In situ hybridization leads to a more severe degradation of the native structure, although it is still possible to correlate the optical signal with the topography of the hybridized chromosome. Key words : atomic force microscope, AFM, chromosomes, C-banding, in situ hybridization.