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1
Gasser, Susan M. "Chromosome Structure: Coiling up chromosomes." Current Biology 5, no. 4 (April 1995): 357–60. http://dx.doi.org/10.1016/s0960-9822(95)00071-6.
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Liehr, Thomas. "From Human Cytogenetics to Human Chromosomics." International Journal of Molecular Sciences 20, no. 4 (February 14, 2019): 826. http://dx.doi.org/10.3390/ijms20040826.
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Background: The concept of “chromosomics” was introduced by Prof. Uwe Claussen in 2005. Herein, the growing insights into human chromosome structure finally lead to a “chromosomic view” of the three-dimensional constitution and plasticity of genes in interphase nuclei are discussed. This review is dedicated to the memory of Prof. Uwe Claussen (30 April 1945–20 July 2008). Recent findings: Chromosomics is the study of chromosomes, their three-dimensional positioning in the interphase nucleus, the consequences from plasticity of chromosomal subregions and gene interactions, the influence of chromatin-modification-mediated events on cells, and even individuals, evolution, and disease. Progress achieved in recent years is summarized, including the detection of chromosome-chromosome-interactions which, if damaged, lead to malfunction and disease. However, chromosomics in the Human Genetics field is not progressing presently, as research interest has shifted from single cell to high throughput, genomic approaches. Conclusion: Chromosomics and its impact were predicted correctly in 2005 by Prof. Claussen. Although some progress was achieved, present reconsiderations of the role of the chromosome and the single cell in Human Genetic research are urgently necessary.
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Anderson, Lorinda K., Naser Salameh, Hank W. Bass, Lisa C. Harper, W. Z. Cande, Gerd Weber, and Stephen M. Stack. "Integrating Genetic Linkage Maps With Pachytene Chromosome Structure in Maize." Genetics 166, no. 4 (April 1, 2004): 1923–33. http://dx.doi.org/10.1093/genetics/166.4.1923.
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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.
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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, no. 16 (August 15, 2001): 5667–77. http://dx.doi.org/10.1128/mcb.21.16.5667-5677.2001.
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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.
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Pizzaia, Daniel, Vanessa M. Oliveira-Maekawa, Aline R. Martins, Mateus Mondin, and Margarida L. R. Aguiar-Perecin. "Karyotype structure and NOR activity in Brazilian Smilax Linnaeus, 1753 species (Smilacaceae)." Comparative Cytogenetics 13, no. 3 (August 22, 2019): 245–63. http://dx.doi.org/10.3897/compcytogen.v13i3.35775.
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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.
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Sajid, Atiqa, El-Nasir Lalani, Bo Chen, Teruo Hashimoto, Darren K. Griffin, Archana Bhartiya, George Thompson, Ian K. Robinson, and Mohammed Yusuf. "Ultra-Structural Imaging Provides 3D Organization of 46 Chromosomes of a Human Lymphocyte Prophase Nucleus." International Journal of Molecular Sciences 22, no. 11 (June 1, 2021): 5987. http://dx.doi.org/10.3390/ijms22115987.
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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.
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Howe, Mary, Kent L. McDonald, Donna G. Albertson, and Barbara J. Meyer. "Him-10 Is Required for Kinetochore Structure and Function on Caenorhabditis elegans Holocentric Chromosomes." Journal of Cell Biology 153, no. 6 (June 11, 2001): 1227–38. http://dx.doi.org/10.1083/jcb.153.6.1227.
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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.
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Spell, R. M., and C. Holm. "Nature and distribution of chromosomal intertwinings in Saccharomyces cerevisiae." Molecular and Cellular Biology 14, no. 2 (February 1994): 1465–76. http://dx.doi.org/10.1128/mcb.14.2.1465-1476.1994.
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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.
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Spell, R. M., and C. Holm. "Nature and distribution of chromosomal intertwinings in Saccharomyces cerevisiae." Molecular and Cellular Biology 14, no. 2 (February 1994): 1465–76. http://dx.doi.org/10.1128/mcb.14.2.1465.
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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.
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Uchida, Tetsuya, Naoto Ishihara, Hiroyuki Zenitani, Keiichiro Hiratsu, and Haruyasu Kinashi. "Circularized Chromosome with a Large Palindromic Structure in Streptomyces griseus Mutants." Journal of Bacteriology 186, no. 11 (June 1, 2004): 3313–20. http://dx.doi.org/10.1128/jb.186.11.3313-3320.2004.
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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.
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Gunawardena, S., E. Heddle, and M. C. Rykowski. "‘Chromosomal puffing’ in diploid nuclei of Drosophila melanogaster." Journal of Cell Science 108, no. 5 (May 1, 1995): 1863–72. http://dx.doi.org/10.1242/jcs.108.5.1863.
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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.
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Al-Ardi, Musafer. "Illumination on the structure and characteristics of Entamoeba histolytica genome." Al-Qadisiyah Journal Of Pure Science 26, no. 4 (July 5, 2021): 19–26. http://dx.doi.org/10.29350/qjps.2021.26.4.1311.
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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.
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Wolf, Klaus Werner, Karel Novák, and František Marec. "Chromosome structure in spermatogenesis of Anabolia furcata (Trichoptera)." Genome 35, no. 1 (February 1, 1992): 46–52. http://dx.doi.org/10.1139/g92-008.
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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.
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Albert, Patrice S., Tao Zhang, Kassandra Semrau, Jean-Marie Rouillard, Yu-Hsin Kao, Chung-Ju Rachel Wang, Tatiana V. Danilova, Jiming Jiang, and James A. Birchler. "Whole-chromosome paints in maize reveal rearrangements, nuclear domains, and chromosomal relationships." Proceedings of the National Academy of Sciences 116, no. 5 (January 17, 2019): 1679–85. http://dx.doi.org/10.1073/pnas.1813957116.
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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.
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Zakian, V. A., H. M. Blanton, L. Wetzel, and G. M. Dani. "Size threshold for Saccharomyces cerevisiae chromosomes: generation of telocentric chromosomes from an unstable minichromosome." Molecular and Cellular Biology 6, no. 3 (March 1986): 925–32. http://dx.doi.org/10.1128/mcb.6.3.925-932.1986.
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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.
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Zakian, V. A., H. M. Blanton, L. Wetzel, and G. M. Dani. "Size threshold for Saccharomyces cerevisiae chromosomes: generation of telocentric chromosomes from an unstable minichromosome." Molecular and Cellular Biology 6, no. 3 (March 1986): 925–32. http://dx.doi.org/10.1128/mcb.6.3.925.
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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.
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Dwiranti, Astari, Hideaki Takata, and Kiichi Fukui. "Reversible Changes of Chromosome Structure upon Different Concentrations of Divalent Cations." Microscopy and Microanalysis 25, no. 3 (April 17, 2019): 817–21. http://dx.doi.org/10.1017/s1431927619000266.
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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+.
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McMaster, Terence J., Mervyn J. Miles, Mark O. Winfield, and Angela Karp. "Analysis off cereal chromosomes by atomic force microscopy." Genome 39, no. 2 (April 1, 1996): 439–44. http://dx.doi.org/10.1139/g96-055.
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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.
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Liu, Wan-Sheng. "Mammalian Sex Chromosome Structure, Gene Content, and Function in Male Fertility." Annual Review of Animal Biosciences 7, no. 1 (February 15, 2019): 103–24. http://dx.doi.org/10.1146/annurev-animal-020518-115332.
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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.
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Sharbel, Timothy F., David M. Green, and Andreas Houben. "B-chromosome origin in the endemic New Zealand frog Leiopelma hochstetteri through sex chromosome devolution." Genome 41, no. 1 (February 1, 1998): 14–22. http://dx.doi.org/10.1139/g97-091.
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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.
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Hasegawa, Koichi, Manuel M. Mota, Kazuyoshi Futai, and Johji Miwa. "Chromosome structure and behaviour in Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae) germ cells and early embryo." Nematology 8, no. 3 (2006): 425–34. http://dx.doi.org/10.1163/156854106778493475.
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AbstractChromosome structure and behaviour in both meiosis of the germ cells and mitosis of the embryo from fertilisation to the two-cell stage in Bursaphelenchus xylophilus were examined by DAPI staining and three-dimensional reconstruction of serial-section images from confocal laser-scanning microscopy. By this method, each chromosome's shape and behaviour were clearly visible in early embryogenesis from fertilisation through the formation and fusion of the male and female pronuclei to the first mitotic division. The male pronucleus was bigger than that of the female, although the oocyte is larger and richer in nutrients than the sperm. From the shape of the separating chromosomes at anaphase, the mitotic chromosomes appeared to be polycentric or holocentric rather than monocentric. Each chromosome was clearly distinguishable in the male and female germ cells, pronuclei of the one-cell stage embryo, and the early embryonic nuclei. The haploid number of chromosomes (N) was six (2n = 12), and all chromosomes appeared similar. The chromosome pair containing the ribosomal RNA-coding site was visualised by fluorescence in situ hybridisation. Unlike the sex determination system in Caenorhabditis elegans (XX in hermaphrodite and XO in male), the system for B. xylophilus may consist of an XX female and an XY male.
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Zhao, Jian, Shaobo Jin, and Shui Hao. "The substructural organization of the chromosome core (scaffold) in meiotic chromosomes of Trilophidia annulata." Genetical Research 64, no. 3 (December 1994): 209–15. http://dx.doi.org/10.1017/s0016672300032869.
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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.
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Eidelman, Yuri, Ilya Salnikov, Svetlana Slanina, and Sergey Andreev. "Chromosome Folding Promotes Intrachromosomal Aberrations under Radiation- and Nuclease-Induced DNA Breakage." International Journal of Molecular Sciences 22, no. 22 (November 10, 2021): 12186. http://dx.doi.org/10.3390/ijms222212186.
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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.
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Li, Ziang, Yunfei Bi, Xing Wang, Yunzhu Wang, Shuqiong Yang, Zhentao Zhang, Jinfeng Chen, and Qunfeng Lou. "Chromosome identification in Cucumis anguria revealed by cross-species single-copy gene FISH." Genome 61, no. 6 (June 2018): 397–404. http://dx.doi.org/10.1139/gen-2017-0235.
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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.
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Matsunaga, Sachihiro, and Kiichi Fukui. "The chromosome peripheral proteins play an active role in chromosome dynamics." BioMolecular Concepts 1, no. 2 (August 1, 2010): 157–64. http://dx.doi.org/10.1515/bmc.2010.018.
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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.
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Csonka, E., I. Cserpan, K. Fodor, G. Hollo, R. Katona, J. Kereso, T. Praznovszky, et al. "Novel generation of human satellite DNA-based artificial chromosomes in mammalian cells." Journal of Cell Science 113, no. 18 (September 15, 2000): 3207–16. http://dx.doi.org/10.1242/jcs.113.18.3207.
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An in vivo approach has been developed for generation of artificial chromosomes, based on the induction of intrinsic, large-scale amplification mechanisms of mammalian cells. Here, we describe the successful generation of prototype human satellite DNA-based artificial chromosomes via amplification-dependent de novo chromosome formations induced by integration of exogenous DNA sequences into the centromeric/rDNA regions of human acrocentric chromosomes. Subclones with mitotically stable de novo chromosomes were established, which allowed the initial characterization and purification of these artificial chromosomes. Because of the low complexity of their DNA content, they may serve as a useful tool to study the structure and function of higher eukaryotic chromosomes. Human satellite DNA-based artificial chromosomes containing amplified satellite DNA, rDNA, and exogenous DNA sequences were heterochromatic, however, they provided a suitable chromosomal environment for the expression of the integrated exogenous genetic material. We demonstrate that induced de novo chromosome formation is a reproducible and effective methodology in generating artificial chromosomes from predictable sequences of different mammalian species. Satellite DNA-based artificial chromosomes formed by induced large-scale amplifications on the short arm of human acrocentric chromosomes may become safe or low risk vectors in gene therapy.
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Brinkley, B. R., and 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 (August 1991): 12–13. http://dx.doi.org/10.1017/s0424820100084363.
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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.
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Dwiranti, Astari, Tohru Hamano, Hideaki Takata, Shoko Nagano, Hongxuan Guo, Keiko Onishi, Toshiyuki Wako, Susumu Uchiyama, and Kiichi Fukui. "The Effect of Magnesium Ions on Chromosome Structure as Observed by Helium Ion Microscopy." Microscopy and Microanalysis 20, no. 1 (November 14, 2013): 184–88. http://dx.doi.org/10.1017/s1431927613013792.
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AbstractOne of the few conclusions known about chromosome structure is that Mg2+is required for the organization of chromosomes. Scanning electron microscopy is a powerful tool for studying chromosome morphology, but being nonconductive, chromosomes require metal/carbon coating that may conceal information about the detailed surface structure of the sample. Helium ion microscopy (HIM), which has recently been developed, does not require sample coating due to its charge compensation system. Here we investigated the structure of isolated human chromosomes under different Mg2+concentrations by HIM. High-contrast and resolution images from uncoated samples obtained by HIM enabled investigation on the effects of Mg2+on chromosome structure. Chromatin fiber information was obtained more clearly with uncoated than coated chromosomes. Our results suggest that both overall features and detailed structure of chromatin are significantly affected by different Mg2+concentrations. Chromosomes were more condensed and a globular structure of chromatin with 30 nm diameter was visualized with 5 mM Mg2+treatment, while 0 mM Mg2+resulted in a less compact and more fibrous structure 11 nm in diameter. We conclude that HIM is a powerful tool for investigating chromosomes and other biological samples without requiring metal/carbon coating.
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Glass, J. R., and L. Gerace. "Lamins A and C bind and assemble at the surface of mitotic chromosomes." Journal of Cell Biology 111, no. 3 (September 1, 1990): 1047–57. http://dx.doi.org/10.1083/jcb.111.3.1047.
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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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Guerra, Marcelo, and Miguel A. García. "Heterochromatin and rDNA sites distribution in the holocentric chromosomes of Cuscuta approximata Bab. (Convolvulaceae)." Genome 47, no. 1 (January 1, 2004): 134–40. http://dx.doi.org/10.1139/g03-098.
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Cuscuta is a widely distributed genus of holoparasitic plants. Holocentric chromosomes have been reported only in species of one of its subgenera (Cuscuta subg. Cuscuta). In this work, a representative of this subgenus, Cuscuta approximata, was investigated looking for its mitotic and meiotic chromosome behaviour and the heterochromatin distribution. The mitotic chromosomes showed neither primary constriction nor Rabl orientation whereas the meiotic ones exhibited the typical quadripartite structure characteristic of holocentrics, supporting the assumption of holocentric chromosomes as a synapomorphy of Cuscuta subg. Cuscuta. Chromosomes and interphase nuclei displayed many heterochromatic blocks that stained deeply with hematoxylin, 4',6-diamidino-2-phenylindole (DAPI), or after C banding. The banded karyotype showed terminal or subterminal bands in all chromosomes and central bands in some of them. The single pair of 45S rDNA sites was observed at the end of the largest chromosome pair, close to a DAPI band and a 5S rDNA site. Two other 5S rDNA site pairs were found, both closely associated with DAPI bands. The noteworthy giant nuclei of glandular cells of petals and ovary wall exhibited large chromocentres typical of polytenic nuclei. The chromosomal location of heterochromatin and rDNA sites and the structure of the endoreplicated nuclei of C. approximata seemed to be similar to those known in monocentric nuclei, suggesting that centromeric organization has little or no effect on chromatin organization.Key words: Cuscuta, holocentric chromosomes, heterochromatin.
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Semeshin, V. F., I. F. Zhimulev, D. Kritikou, and A. Zacharopoulou. "Electron microscope investigation of polytene chromosomes in the Mediterranean fruit fly Ceratitis capitata." Genome 38, no. 4 (August 1, 1995): 652–60. http://dx.doi.org/10.1139/g95-083.
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Ultrastructural analyses of polytene chromosomes from male pupal orbital bristle cells and from larval salivary glands of Ceratitis capitata were carried out. It was shown that chromatin complexes corresponding to the X chromosome heterochromatic network are surrounded by material containing ribonucleoprotein (RNP) granules 250–300 Å (1 Å = 0.1 nm) in diameter. RNP granules of similar size surround the spherical Y chromosome. These data point out the presence of transcriptional activity in both of these chromosomes. The absence of clear structure in chromosomal regions situated between large bands in both types of tissues was observed. These results support the hypothesis of weak synapsis between chromatids or small chromomeres of polytene chromosomes in this species. In addition, we describe a specific puff revealed in both orbital trichogen cells and salivary glands that is morphologically similar to the 93D puff of Drosophila melanogaster.Key words: Ceratitis capitata, polytene chromosomes, electron microscopy.
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Houchmandzadeh, Bahram, and Stefan Dimitrov. "Elasticity Measurements Show the Existence of Thin Rigid Cores Inside Mitotic Chromosomes." Journal of Cell Biology 145, no. 2 (April 19, 1999): 215–23. http://dx.doi.org/10.1083/jcb.145.2.215.
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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.
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McNally, Karen P., Elizabeth A. Beath, Brennan M. Danlasky, Consuelo Barroso, Ting Gong, Wenzhe Li, Enrique Martinez-Perez, and Francis J. McNally. "Cohesin is required for meiotic spindle assembly independent of its role in cohesion in C. elegans." PLOS Genetics 18, no. 10 (October 24, 2022): e1010136. http://dx.doi.org/10.1371/journal.pgen.1010136.
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Accurate chromosome segregation requires a cohesin-mediated physical attachment between chromosomes that are to be segregated apart, and a bipolar spindle with microtubule plus ends emanating from exactly two poles toward the paired chromosomes. We asked whether the striking bipolar structure of C. elegans meiotic chromosomes is required for bipolarity of acentriolar female meiotic spindles by time-lapse imaging of mutants that lack cohesion between chromosomes. Both a spo-11 rec-8 coh-4 coh-3 quadruple mutant and a spo-11 rec-8 double mutant entered M phase with separated sister chromatids lacking any cohesion. However, the quadruple mutant formed an apolar spindle whereas the double mutant formed a bipolar spindle that segregated chromatids into two roughly equal masses. Residual non-cohesive COH-3/4-dependent cohesin on separated sister chromatids of the double mutant was sufficient to recruit haspin-dependent Aurora B kinase, which mediated bipolar spindle assembly in the apparent absence of chromosomal bipolarity. We hypothesized that cohesin-dependent Aurora B might activate or inhibit spindle assembly factors in a manner that would affect their localization on chromosomes and found that the chromosomal localization patterns of KLP-7 and CLS-2 correlated with Aurora B loading on chromosomes. These results demonstrate that cohesin is essential for spindle assembly and chromosome segregation independent of its role in sister chromatid cohesion.
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Umezu, Keiko, Mina Hiraoka, Masaaki Mori, and Hisaji Maki. "Structural Analysis of Aberrant Chromosomes That Occur Spontaneously in Diploid Saccharomyces cerevisiae: Retrotransposon Ty1 Plays a Crucial Role in Chromosomal Rearrangements." Genetics 160, no. 1 (January 1, 2002): 97–110. http://dx.doi.org/10.1093/genetics/160.1.97.
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Abstract The structural analysis of aberrant chromosomes is important for our understanding of the molecular mechanisms underlying chromosomal rearrangements. We have identified a number of diploid Saccharomyces cerevisiae clones that have undergone loss of heterozygosity (LOH) leading to functional inactivation of the hemizygous URA3 marker placed on the right arm of chromosome III. Aberrant-sized chromosomes derived from chromosome III were detected in ~8% of LOH clones. Here, we have analyzed the structure of the aberrant chromosomes in 45 LOH clones with a PCR-based method that determines the ploidy of a series of loci on chromosome III. The alterations included various deletions and amplifications. Sequencing of the junctions revealed that all the breakpoints had been made within repeat sequences in the yeast genome, namely, MAT-HMR, which resulted in intrachromosomal deletion, and retrotransposon Ty1 elements, which were involved in various translocations. Although the translocations involved different breakpoints on different chromosomes, all breakpoints were exclusively within Ty1 elements. Some of the resulting Ty1 elements left at the breakpoints had a complex construction that indicated the involvement of other Ty1 elements not present at the parental breakpoints. These indicate that Ty1 elements are crucially involved in the generation of chromosomal rearrangements in diploid yeast cells.
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Meng, Zhuang, Xiaoxu Hu, Zhiliang Zhang, Zhanjie Li, Qingfang Lin, Mei Yang, Pingfang Yang, Ray Ming, Qingyi Yu, and Kai Wang. "Chromosome Nomenclature and Cytological Characterization of Sacred Lotus." Cytogenetic and Genome Research 153, no. 4 (2017): 223–31. http://dx.doi.org/10.1159/000486777.
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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.
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Benedetti, Fabrizio, Julien Dorier, Yannis Burnier, and Andrzej Stasiak. "Models that include supercoiling of topological domains reproduce several known features of interphase chromosomes." Nucleic Acids Research 42, no. 5 (December 22, 2013): 2848–55. http://dx.doi.org/10.1093/nar/gkt1353.
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Abstract Understanding the structure of interphase chromosomes is essential to elucidate regulatory mechanisms of gene expression. During recent years, high-throughput DNA sequencing expanded the power of chromosome conformation capture (3C) methods that provide information about reciprocal spatial proximity of chromosomal loci. Since 2012, it is known that entire chromatin in interphase chromosomes is organized into regions with strongly increased frequency of internal contacts. These regions, with the average size of ∼1 Mb, were named topological domains. More recent studies demonstrated presence of unconstrained supercoiling in interphase chromosomes. Using Brownian dynamics simulations, we show here that by including supercoiling into models of topological domains one can reproduce and thus provide possible explanations of several experimentally observed characteristics of interphase chromosomes, such as their complex contact maps.
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Mellone, Barbara G. "Structural and temporal regulation of centromeric chromatinThis paper is one of a selection of papers published in this Special Issue, entitled 29th Annual International Asilomar Chromatin and Chromosomes Conference, and has undergone the Journal’s usual peer review process." Biochemistry and Cell Biology 87, no. 1 (February 2009): 255–64. http://dx.doi.org/10.1139/o08-121.
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Normal inheritance of genetic material requires that chromosomes segregate faithfully during mitosis and meiosis. The kinetochore is a unique structure that attaches chromosomes to the microtubule spindle, monitors proper chromosome attachment to the spindle through the mitotic checkpoint, and couples spindle and motor protein forces to move chromosomes during prometaphase and anaphase. The centromere is a specialized chromosomal site that is the structural and functional foundation for kinetochore formation, and is characterized by a unique type of chromatin that needs to be reconstituted after each replication cycle. In this review, recent progress in understanding the structural nature of this chromatin and how it is specifically maintained through cell division are discussed.
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Danieli, Adi, and Argyris Papantonis. "Spatial genome architecture and the emergence of malignancy." Human Molecular Genetics 29, R2 (July 3, 2020): R197—R204. http://dx.doi.org/10.1093/hmg/ddaa128.
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Abstract Human chromosomes are large spatially and hierarchically structured entities, the integrity of which needs to be preserved throughout the lifespan of the cell and in conjunction with cell cycle progression. Preservation of chromosomal structure is important for proper deployment of cell type-specific gene expression programs. Thus, aberrations in the integrity and structure of chromosomes will predictably lead to disease, including cancer. Here, we provide an updated standpoint with respect to chromatin misfolding and the emergence of various cancer types. We discuss recent studies implicating the disruption of topologically associating domains, switching between active and inactive compartments, rewiring of promoter–enhancer interactions in malignancy as well as the effects of single nucleotide polymorphisms in non-coding regions involved in long-range regulatory interactions. In light of these findings, we argue that chromosome conformation studies may now also be useful for patient diagnosis and drug target discovery.
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Houchmandzadeh, Bahram, John F. Marko, Didier Chatenay, and Albert Libchaber. "Elasticity and Structure of Eukaryote Chromosomes Studied by Micromanipulation and Micropipette Aspiration." Journal of Cell Biology 139, no. 1 (October 6, 1997): 1–12. http://dx.doi.org/10.1083/jcb.139.1.1.
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The structure of mitotic chromosomes in cultured newt lung cells was investigated by a quantitative study of their deformability, using micropipettes. Metaphase chromosomes are highly extensible objects that return to their native shape after being stretched up to 10 times their normal length. Larger deformations of 10 to 100 times irreversibly and progressively transform the chromosomes into a “thin filament,” parts of which display a helical organization. Chromosomes break for elongations of the order of 100 times, at which time the applied force is around 100 nanonewtons. We have also observed that as mitosis proceeds from nuclear envelope breakdown to metaphase, the native chromosomes progressively become more flexible. (The elastic Young modulus drops from 5,000 ± 1,000 to 1,000 ± 200 Pa.) These observations and measurements are in agreement with a helix-hierarchy model of chromosome structure. Knowing the Young modulus allows us to estimate that the force exerted by the spindle on a newt chromosome at anaphase is roughly one nanonewton.
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Jesionek, Wojciech, Markéta Bodláková, Zdeněk Kubát, Radim Čegan, Boris Vyskot, Jan Vrána, Jan Šafář, Janka Puterova, and Roman Hobza. "Fundamentally different repetitive element composition of sex chromosomes in Rumex acetosa." Annals of Botany 127, no. 1 (September 9, 2020): 33–47. http://dx.doi.org/10.1093/aob/mcaa160.
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Abstract Background and Aims Dioecious species with well-established sex chromosomes are rare in the plant kingdom. Most sex chromosomes increase in size but no comprehensive analysis of the kind of sequences that drive this expansion has been presented. Here we analyse sex chromosome structure in common sorrel (Rumex acetosa), a dioecious plant with XY1Y2 sex determination, and we provide the first chromosome-specific repeatome analysis for a plant species possessing sex chromosomes. Methods We flow-sorted and separately sequenced sex chromosomes and autosomes in R. acetosa using the two-dimensional fluorescence in situ hybridization in suspension (FISHIS) method and Illumina sequencing. We identified and quantified individual repeats using RepeatExplorer, Tandem Repeat Finder and the Tandem Repeats Analysis Program. We employed fluorescence in situ hybridization (FISH) to analyse the chromosomal localization of satellites and transposons. Key Results We identified a number of novel satellites, which have, in a fashion similar to previously known satellites, significantly expanded on the Y chromosome but not as much on the X or on autosomes. Additionally, the size increase of Y chromosomes is caused by non-long terminal repeat (LTR) and LTR retrotransposons, while only the latter contribute to the enlargement of the X chromosome. However, the X chromosome is populated by different LTR retrotransposon lineages than those on Y chromosomes. Conclusions The X and Y chromosomes have significantly diverged in terms of repeat composition. The lack of recombination probably contributed to the expansion of diverse satellites and microsatellites and faster fixation of newly inserted transposable elements (TEs) on the Y chromosomes. In addition, the X and Y chromosomes, despite similar total counts of TEs, differ significantly in the representation of individual TE lineages, which indicates that transposons proliferate preferentially in either the paternal or the maternal lineage.
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HOLMQUIST, G. P. "Structure of Chromosomes." Science 252, no. 5011 (June 7, 1991): 1437–38. http://dx.doi.org/10.1126/science.252.5011.1437-a.
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Hołówka, Joanna, and Małgorzata Płachetka. "Structure of bacterial chromosome: An analysis of DNA-protein interactions in vivo." Postępy Higieny i Medycyny Doświadczalnej 71 (December 8, 2017): 0. http://dx.doi.org/10.5604/01.3001.0010.6696.
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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.
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Liu, Mao-Sen, Shih-Hsuan Tseng, Ching-Chi Tsai, Ting-Chu Chen, and Mei-Chu Chung. "Chromosomal variations of Lycoris species revealed by FISH with rDNAs and centromeric histone H3 variant associated DNAs." PLOS ONE 16, no. 9 (September 30, 2021): e0258028. http://dx.doi.org/10.1371/journal.pone.0258028.
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Lycoris species have various chromosome numbers and karyotypes, but all have a constant total number of chromosome major arms. In addition to three fundamental types, including metacentric (M-), telocentric (T-), and acrocentric (A-) chromosomes, chromosomes in various morphology and size were also observed in natural populations. Both fusion and fission translocation have been considered as main mechanisms leading to the diverse karyotypes among Lycoris species, which suggests the centromere organization playing a role in such arrangements. We detected several chromosomal structure changes in Lycoris including centric fusion, inversion, gene amplification, and segment deletion by using fluorescence in situ hybridization (FISH) probing with rDNAs. An antibody against centromere specific histone H3 (CENH3) of L. aurea (2n = 14, 8M+6T) was raised and used to obtain CENH3-associated DNA sequences of L. aurea by chromatin immunoprecipitation (ChIP) cloning method. Immunostaining with anti-CENH3 antibody could label the centromeres of M-, T-, and A-type chromosomes. Immunostaining also revealed two centromeres on one T-type chromosome and a centromere on individual mini-chromosome. Among 10,000 ChIP clones, 500 clones which showed abundant in L. aurea genome by dot-blotting analysis were FISH mapped on chromosomes to examine their cytological distribution. Five of these 500 clones could generate intense FISH signals at centromeric region on M-type but not T-type chromosomes. FISH signals of these five clones rarely appeared on A-type chromosomes. The five ChIP clones showed similarity in DNA sequences and could generate similar but not identical distribution patterns of FISH signals on individual chromosomes. Furthermore, the distinct distribution patterns of FISH signals on each chromosome generated by these five ChIP clones allow to identify individual chromosome, which is considered difficult by conventional staining approaches. Our results suggest a different organization of centromeres of the three chromosome types in Lycoris species.
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Meyer, Barbara J. "Sex and death: from cell fate specification to dynamic control of X-chromosome structure and gene expression." Molecular Biology of the Cell 29, no. 22 (November 2018): 2616–21. http://dx.doi.org/10.1091/mbc.e18-06-0397.
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Determining sex is a binary developmental decision that most metazoans must make. Like many organisms, Caenorhabditis elegans specifies sex (XO male or XX hermaphrodite) by tallying X-chromosome number. We dissected this precise counting mechanism to determine how tiny differences in concentrations of signals are translated into dramatically different developmental fates. Determining sex by counting chromosomes solved one problem but created another—an imbalance in X gene products. We found that nematodes compensate for the difference in X-chromosome dose between sexes by reducing transcription from both hermaphrodite X chromosomes. In a surprising feat of evolution, X-chromosome regulation is functionally related to a structural problem of all mitotic and meiotic chromosomes: achieving ordered compaction of chromosomes before segregation. We showed the dosage compensation complex is a condensin complex that imposes a specific three-dimensional architecture onto hermaphrodite X chromosomes. It also triggers enrichment of histone modification H4K20me1. We discovered the machinery and mechanism underlying H4K20me1 enrichment and demonstrated its pivotal role in regulating higher-order X-chromosome structure and gene expression.
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Typylo, K. "Karyotype variability of the Ukrainian Mountain-Carpathian sheep breed." Agricultural Science and Technology 12, no. 1 (March 2020): 3–5. http://dx.doi.org/10.15547/ast.2020.01.001.
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Abstract. The main purpose of this work was to describe the karyotype variability of the Ukrainian Mountain-Carpathian sheep breed. Cytogenetic studies were carried out on a group of 25 sheep from that breed. The cultivation of lymphocytes, preparing the cytogenetic samples, classification and registration of chromosome aberrations were held using conventional methods. It was established that the number and structure of the chromosomes of sheep of the Ukrainian Mountain-Carpathian breed correspond to the norm typical for this species of animals. Chromosomal variability of the studied population includes 19.22% of numerical and structural aberrations. By the number and structure of the chromosome set the Ukrainian Mountain-Carpathian sheep breed does not differ from other breeds of sheep. Accurate identification of individual chromosomes with routine coloring allows using cytogenetic studies in breeding practice in sheep breeding.
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Roslan, Nurzanariah, Karmila Kamil, and 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, no. 3 (March 31, 2014): 92–107. http://dx.doi.org/10.31686/ijier.vol2.iss3.158.
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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.
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Liang, Jiangtao, Simon M. Bondarenko, Igor V. Sharakhov, and Maria V. Sharakhova. "Visualization of the Linear and Spatial Organization of Chromosomes in Mosquitoes." Cold Spring Harbor Protocols 2022, no. 12 (August 5, 2022): pdb.top107732. http://dx.doi.org/10.1101/pdb.top107732.
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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.
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Poirier, Michael G., Sertac Eroglu, and John F. Marko. "The Bending Rigidity of Mitotic Chromosomes." Molecular Biology of the Cell 13, no. 6 (June 2002): 2170–79. http://dx.doi.org/10.1091/mbc.01-08-0401.
Full textAbstract:
The bending rigidities of mitotic chromosomes isolated from cultured N. viridescens (newt) and Xenopusepithelial cells were measured by observing their spontaneous thermal bending fluctuations. When combined with simultaneous measurement of stretching elasticity, these measurements constrain models for higher order mitotic chromosome structure. We measured bending rigidities of B ∼10−22 N · m2 for newt and ∼10−23 N · m2 forXenopus chromosomes extracted from cells. A similar bending rigidity was measured for newt chromosomes in vivo by observing bending fluctuations in metaphase-arrested cells. Following each bending rigidity measurement, a stretching (Young's) modulus of the same chromosome was measured in the range of 102 to 103 Pa for newt and Xenopus chromosomes. For each chromosome, these values of B and Y are consistent with those expected for a simple elastic rod, B ≈ YR4, where R is the chromosome cross-section radius. Our measurements rule out the possibility that chromosome stretching and bending elasticity are principally due to a stiff central core region and are instead indicative of an internal structure, which is essentially homogeneous in its connectivity across the chromosome cross-section.
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Jeppesen, Peter. "Immunofluorescence in cytogenetic analysis: method and applications." Genetics and Molecular Biology 23, no. 4 (December 2000): 1107–14. http://dx.doi.org/10.1590/s1415-47572000000400059.
Full textAbstract:
Control of the genetic information encoded by DNA in mammalian chromosomes is mediated by proteins, some of which are only transiently attached, although others are intrinsically associated with nucleic acid in the complex mixture known as chromatin. Chromatin-associated proteins range from the ubiquitous and abundant histones down to the most specific and rare of transcription factors. Although many chromatin proteins are probably excluded from highly condensed mitotic chromosomes, a number are retained throughout the cell cycle and can be detected on chromosomes in metaphase spreads. Comparing the distribution of a chromosomal protein with known cytogenetic markers on metaphase chromosomes can provide an important and potentially highly informative first source of data on the function of the protein under consideration. The aim of the present study is to summarize some of the principles involved in obtaining suitable chromosome preparations for subsequent immunolocalization of protein antigens. Some applications of the method will be included to illustrate how this approach has increased our understanding of chromosome structure and genetic regulation.
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Hamano, Tohru, Astari Dwiranti, Kohei Kaneyoshi, Shota Fukuda, Reo Kometani, Masayuki Nakao, Hideaki Takata, Susumu Uchiyama, Nobuko Ohmido, and Kiichi Fukui. "Chromosome Interior Observation by Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) Using Ionic Liquid Technique." Microscopy and Microanalysis 20, no. 5 (July 10, 2014): 1340–47. http://dx.doi.org/10.1017/s143192761401280x.
Full textAbstract:
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.