Bibliographies thématiques / Heterochromatin polymorphism

Littérature scientifique sur le sujet « Heterochromatin polymorphism »

Auteur : Grafiati
Publié le 18 mai 2024

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Articles de revues sur le sujet "Heterochromatin polymorphism"

1

Hatsumi, Machiko. « Karyotype polymorphism in Drosophila albomicans ». Genome 29, no 3 (1 juin 1987) : 395–400. http://dx.doi.org/10.1139/g87-069.

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Supernumerary (B) chromosomes are present in Thai, Malay, and Burmese populations of Drosophila albomicans (2n = 6) in a polymorphic state. Although usually stable at mitosis, their numbers differed between individuals and their frequency was also different between isofemale lines and between populations. Arm 3 of the X3 chromosome was polymorphic for the presence and the size of a procentric heterochromatic segment. Chromosome 4 is polytypic for variation in length governed by differences in the amount of heterochromatin and the long variant is polymorphic for the location of its secondary constriction. Key words: Drosophila albomicans, karyotype polymorphism, B chromosome.
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Taran Kyzy, Jafar Aliyev. « Value heterochromatin and polymorphic varian gene folat cycle in women with miscarried and losses of pregnancy ». HEALTH OF WOMAN, no 9(115) (30 novembre 2016) : 148–51. http://dx.doi.org/10.15574/hw.2016.115.148.

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The article presents data from surveys of women of losses of pregnancy (LP) in history, conducted within the medical genetic counseling, given the urgency of specifying genetic factors that actually are in causal connection with the LP specification clinical effects of epigenetic variability. The objective: to clarify the meaning of the changes in women heterochromatin (chromosomal polymorphism) and polymorphic variants of genes folat cycle enzymes as potential risk factors and pathogenic primordial LP. Patients and methods. The study involved two groups of women: I - 154 observations with complicated obstetric history in LP and II - 32 healthy women with uncomplicated reproductive history, held preconception planning to prevent pregnancy. Studied genealogical history, especially of internal organs, genitalia. Special studies included cytogenetic analysis, identification of gene polymorphisms system folat cycle methylentetrahydrofolate reductase [MTHFR] (C677T, A1298C, G1793A); methionine synthase reductase [MTRR] (A66G). Results. Women with a history of LP in 36.4% identified chromosome polymorphisms (SNPs extreme variants of chromosome polymorphism) on the background of various risk alleles of polymorphic variants of genes folat cycle; 7.1% of them is a polymorphism of the 21st chromosome. These genetic features are interpreted as a significant risk factor for LP as grounds for targeted in-depth medical and genetic examination. Prevalence among women with a history of PL undifferentiated forms cjnnective tissue and mesoderm dysplasia, benign tumors and «precancerous» states, as well as the prevalence of cardiovascular and psycho-neurological disease in pedigree suggests pathogenetic link these phenomena, the role of chromosomal polymorphism and polymorphic variants of genes of pathogenic folat cycle as primordial. Conclusion. The data on the place and role of heterochromatin and gene polymorphisms folat cycle in the origin LP should be mandatory option when examining women within the medical genetic counseling. Key words: pregnancy, reproductive losses, chromosomal instability, folat cycle genes, ancestry.
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Sharma, Atashi, Nicholas A. Kinney, Vladimir A. Timoshevskiy, Maria V. Sharakhova et Igor V. Sharakhov. « Structural Variation of the X Chromosome Heterochromatin in the Anopheles gambiae Complex ». Genes 11, no 3 (19 mars 2020) : 327. http://dx.doi.org/10.3390/genes11030327.

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Heterochromatin is identified as a potential factor driving diversification of species. To understand the magnitude of heterochromatin variation within the Anopheles gambiae complex of malaria mosquitoes, we analyzed metaphase chromosomes in An. arabiensis, An. coluzzii, An. gambiae, An. merus, and An. quadriannulatus. Using fluorescence in situ hybridization (FISH) with ribosomal DNA (rDNA), a highly repetitive fraction of DNA, and heterochromatic Bacterial Artificial Chromosome (BAC) clones, we established the correspondence of pericentric heterochromatin between the metaphase and polytene X chromosomes of An. gambiae. We then developed chromosome idiograms and demonstrated that the X chromosomes exhibit qualitative differences in their pattern of heterochromatic bands and position of satellite DNA (satDNA) repeats among the sibling species with postzygotic isolation, An. arabiensis, An. merus, An. quadriannulatus, and An. coluzzii or An. gambiae. The identified differences in the size and structure of the X chromosome heterochromatin point to a possible role of repetitive DNA in speciation of mosquitoes. We found that An. coluzzii and An. gambiae, incipient species with prezygotic isolation, share variations in the relative positions of the satDNA repeats and the proximal heterochromatin band on the X chromosomes. This previously unknown genetic polymorphism in malaria mosquitoes may be caused by a differential amplification of DNA repeats or an inversion in the sex chromosome heterochromatin.
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Amores, A., G. Martinez, J. Reina et M. C. Alvarez. « Karyotype, C-banding, and Ag-NOR analysis in Diplodus bellottii (Sparidae, Perciforms). Intra-individual polymorphism involving heterochromatic regions ». Genome 36, no 4 (1 août 1993) : 672–75. http://dx.doi.org/10.1139/g93-090.

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A karyotype analysis was carried out in nine specimens of the Sparid species Diplodus bellottii using conventional staining, as well as C-banding and Ag-NOR banding techniques, showing, respectively, 2n = 46 and fundamental number (FN) = 54, and scarce heterochromatic areas irregularly distributed and up to four NOR active regions that were C positive. When compared with the karyotypes of other related species, one centric fusion giving rise to a large metacentric pair and several pericentric inversions seem to have been involved in the karyotype evolution. An intra-individual polymorphism was detected in one specimen, resulting in two karyotypic forms in roughly identical proportion, owing to a larger C-band by the NOR regions, appearing either in a terminal position of the short arms of pair 2 or in telomeric position of pair 3. These findings suggest that the extra heterochromatic segment responsible for the heteromorphism apparently only involves associated heterochromatin and not the NORs themselves. This C-positive block seems to have eventually been transferred between heterologous NOR chromosomes by a somatic event, facilitated by the physical proximity of NOR pairs in the nucleolus.Key words: Sparidae, karyotype, heterochromatin, nucleolus organizers, chromosome polymorphism.
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Asamizu, Erika, Kenta Shirasawa, Hideki Hirakawa, Shusei Sato, Satoshi Tabata, Kentaro Yano, Tohru Ariizumi, Daisuke Shibata et Hiroshi Ezura. « Mapping of Micro-Tom BAC-End Sequences to the Reference Tomato Genome Reveals Possible Genome Rearrangements and Polymorphisms ». International Journal of Plant Genomics 2012 (27 novembre 2012) : 1–8. http://dx.doi.org/10.1155/2012/437026.

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A total of 93,682 BAC-end sequences (BESs) were generated from a dwarf model tomato, cv. Micro-Tom. After removing repetitive sequences, the BESs were similarity searched against the reference tomato genome of a standard cultivar, “Heinz 1706.” By referring to the “Heinz 1706” physical map and by eliminating redundant or nonsignificant hits, 28,804 “unique pair ends” and 8,263 “unique ends” were selected to construct hypothetical BAC contigs. The total physical length of the BAC contigs was 495, 833, 423 bp, covering 65.3% of the entire genome. The average coverage of euchromatin and heterochromatin was 58.9% and 67.3%, respectively. From this analysis, two possible genome rearrangements were identified: one in chromosome 2 (inversion) and the other in chromosome 3 (inversion and translocation). Polymorphisms (SNPs and Indels) between the two cultivars were identified from the BLAST alignments. As a result, 171,792 polymorphisms were mapped on 12 chromosomes. Among these, 30,930 polymorphisms were found in euchromatin (1 per 3,565 bp) and 140,862 were found in heterochromatin (1 per 2,737 bp). The average polymorphism density in the genome was 1 polymorphism per 2,886 bp. To facilitate the use of these data in Micro-Tom research, the BAC contig and polymorphism information are available in the TOMATOMICS database.
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Jouve, Nicolas, Carmen Galindo, Montserrat Mesta, Fernando Diaz, Beatriz Albella, Pilar Garcia et Consuelo Soler. « Changes in triticale chromosome heterochromatin visualized by C-banding ». Genome 32, no 5 (1 octobre 1989) : 735–42. http://dx.doi.org/10.1139/g89-506.

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The distribution and characterization of heterochromatin in a series of cultivars, parents, new amphiploids and progeny of hexaploid triticale were comparatively studied using C-banding and morphometric analysis. A high level of intervarietal polymorphism was detected for the banding pattern. The chromosome pairs 4A and 1R presented the most constant pattern of heterochromatin distribution among 31 triticale lines studied. A total of 126 bands have been catalogued, from which 28, 59, and 39 belong, respectively, to the A, B and R genomes. The ratio of polymorphic bands per genome was 23/28, 36/59, and 30/39. The chromosomes displayed heterochromatin modifications consistent in both presence–absence and relative length of their content per genome, when passed from the parents to the amphiploids. Variations in the heterochromatin were also observed among sister plants coming from crosses between wheat and triticale. The heterochromatin content showed gradual tendencies either to increase or decrease in each genome during successive self-cross generations after that cross. The existence of a systematic process of variation of heterochromatin content in triticale is assumed, and the nature of this phenomenon is discussed.Key words: triticale, tetraploid wheat, rye, C-banding, heterochromatin.
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Mayr, B., G. Geber, H. Auer, M. Kalat et W. Schleger. « Heterochromatin composition and nucleolus organizer activity in four canid species ». Canadian Journal of Genetics and Cytology 28, no 5 (1 octobre 1986) : 744–53. http://dx.doi.org/10.1139/g86-105.

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Sequential staining with a counterstain-contrasted fluorescent banding technique (chromomycin A3 – distamycin A – DAPI) revealed the occurrence of distamycin A – 4,6-diamidino-2-phenylindole (DA–DAPI) staining heterochromatin in the centromeric regions of chromosomes 33, 36, 37, and 38 in the wolf (Canis lupus pallipes) and of chromosomes 13, 16, and 23 in the blue fox (Alopex lagopus). The red fox (Vulpes vulpes) lacked such regions. Staining with DAPI – actinomycin D produced a QFH-type banding pattern with clearcut differences in the staining behaviour of DA–DAPI positive regions between these three canid species. Staining with the fluorochrome D 287/170 did not preferentially highlight any of the DA–DAPI positive regions in any of them. Counterstain-enhanced chromomycin A3 R-banding and studies of nucleolus organizer region location and activity confirmed a close relationship between the karyotype of the wolf and the domestic dog. Few heterochromatic marker bands were encountered in these two species, but heterochromatin polymorphism was evident in the blue fox.Key words: Canidae, heterochromatin, nucleolus organizers.
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Cabrero, Josefa, et Juan Pedro M. Camacho. « Population cytogenetics of Chorthippus vagans. I. Polymorphisms for pericentric inversion and for heterochromatin deletion ». Genome 29, no 2 (1 avril 1987) : 280–84. http://dx.doi.org/10.1139/g87-048.

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Two different polymorphisms have been identified in natural populations of the grasshopper Chorthippus vagans. One of these involved an inversion polymorphism in the M7 chromosome and was present in two populations from Granada. In one of these, from Prados del Pinar, the frequency of this polymorphism was constant over three consecutive generations, and meiotic studies of heterozygous individuals indicated that this inversion had not effect on male fertility. The second polymorphism involved a deletion of the distal C-band of the short arm of the M4 chromosome, which was observed in three different populations. From the observed difference between its frequency in adults and embryos in one of these populations, that of Prados del Pinar, it would appear that this deletion is strongly selected against. Despite this, its frequency was maintained in adult individuals of this population over 2 consecutive years. Complete meiotic drive in favour of the M4–d chromosomes in heterozygous females would explain the maintenance of its frequency despite the fact that it is counterselected. Key words: Chorthippus, inversion, heterochromatin, polymorphism (chromosome), meiotic drive.
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Di Meo, G. P., A. Perucatti, L. Iannuzzi, M. T. Rangel-Figueiredo et L. Ferrara. « Constitutive heterochromatin polymorphism in river buffalo chromosomes ». Caryologia 48, no 2 (janvier 1995) : 137–46. http://dx.doi.org/10.1080/00087114.1995.10797323.

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Ahearn, Jayne N., et Visut Baimai. « Cytogenetic study of three closely related species of Hawaiian Drosophila ». Genome 29, no 1 (1 février 1987) : 47–57. http://dx.doi.org/10.1139/g87-008.

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Three allopatric species from the Hawaiian islands, Drosophila bostrycha (Molokai), D. affinidisjuncta (West Maui), and D. disjuncta (East Maui), are extremely similar in morphology but differ in metaphase chromosomes by the amount and distribution of heterochromatin. Their polytene chromosomes are virtually homosequential with only slight differences at the tip of the microchromosome. Each is polymorphic for one or more inversions, especially in chromsome 4. Salivary gland chromosomes of F1 larvae reared either from wild-caught females or wild-caught males mated to standard laboratory stocks were examined for gene arrangements. Drosophila bostrycha and D. affinidisjuncta share a polymorphism for inversion 4v, which is much more frequent in the latter than in the former. In D. disjuncta 4v has been found only joined in a haplotype with three other inversions (g2 h2 i2) at a low frequency at Kipahulu Valley. Drosophila disjuncta is unique in having another fourth chromosome inversion, 4k, which is highest in frequency at Waikamoi. A new inversion, 2s, was discovered at Uluini Stream. Interspecific hybridizations were carried out in small mass matings. Backcrosses and dissections demonstrated that all F1 females were fertile. All F1 males were sterile in either of two categories with reciprocal hybrids uniformly manifesting one or the other type. Attempts to model the sterility mechanism suggest that more than chromosomal sterility is involved. Our results are discussed in relation to other closely related clusters of species having heterochromatin-based karyotype variations. Key words: heterochromatin, hybrid sterility, inversion, polymorphism, species divergence.
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Thèses sur le sujet "Heterochromatin polymorphism"

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Davison, Jerry. « Polymorphism and replication of heterochromatic repeats in the DNA of Arabidopsis / ». Thesis, Connect to this title online ; UW restricted, 2006. http://hdl.handle.net/1773/5134.

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Doco-Fenzy, Martine. « De l'adn satellite aux satellites chromosomiques : etude du polymorphisme de la structure des bras courts des chromosomes acrocentriques humains par hybridation in situ revelee en fluorescence (doctorat : genie biologique) ». Reims, 1998. http://www.theses.fr/1998REIMM205.

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