Academic literature on the topic 'Organisation des chromosomes'
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Journal articles on the topic "Organisation des chromosomes"
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Grutzner, F., A. Casey, and T. Daish. "105. MEIOTIC ACROBATS: MONOTREME SEX CHROMOSOME ORGANISATION DURING SPERMATOGENESIS." Reproduction, Fertility and Development 22, no. 9 (2010): 23. http://dx.doi.org/10.1071/srb10abs105.
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Monotremes feature an extraordinarily complex sex chromosome system which shares extensive homology with bird sex chromosomes but no homology to sex chromosomes of other mammals (1,2,3). At meiotic prophase I the ten sex chromosomes in platypus (nine in echidna) assemble in a sex chromosome chain. We previously identified the multiple sex chromosomes in platypus and echidna that form the meiotic chain in males (1,2,4). We showed that sex chromosomes assembly in the chain in a specific order (5) and that they segregate alternately (1). In secondary spermatocytes we observed clustering of X and Y chromosomes in sperm (6). Our current research investigates the formation of the synaptonemal complex, recombination and meiotic silencing of monotreme sex chromosomes. Meiotic sex chromosome inactivation (MSCI) has been observed in eutherian mammals, marsupials and birds but has so far not been investigated experimentally in monotremes. We found that during pachytene the X5Y5 end of the chain closely associates with the nucleolus and accumulates repressive chromatin marks (e.g. histone variant mH2A). In contrast to the differential accumulation of mH2A we observe extensive loading of the cohesin SMC3 on sex chromosomes in particular during the pachytene stage of meiotic prophase I. We have also used markers of active transcription and gene expression analysis to investigate gene activity in platypus meiotic cells. I will discuss how these findings contribute to our current understanding of the meiotic organisation of monotreme sex chromosomes and the evolution of MSCI in birds and mammals. (1) Grützner et al. (2004), Nature 432: 913–917.(2) Rens et al. (2007), Genome Biology 16;8(11): R243.(3) Veyrunes et al. (2008), Genome Research, 18(6): 995–1004.(4) Rens et al. (2004), Proceedings of the National Academy of Sciences USA. 101 (46): 16 257–16 261.(5) Daish et al. (2009), Reprod Fertil Dev. 21(8): 976–84.(6) Tsend-Ayush et al. (2009), Chromosoma 118(1): 53–69.
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Joseph, Sunitha, Rebecca O’Connor, Abdullah Al Mutery, Mick Watson, Denis Larkin, and Darren Griffin. "Chromosome Level Genome Assembly and Comparative Genomics between Three Falcon Species Reveals an Unusual Pattern of Genome Organisation." Diversity 10, no. 4 (October 18, 2018): 113. http://dx.doi.org/10.3390/d10040113.
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Whole genome assemblies are crucial for understanding a wide range of aspects of falcon biology, including morphology, ecology, and physiology, and are thus essential for their care and conservation. A key aspect of the genome of any species is its karyotype, which can then be linked to the whole genome sequence to generate a so-called chromosome-level assembly. Chromosome-level assemblies are essential for marker assisted selection and genotype-phenotype correlations in breeding regimes, as well as determining patterns of gross genomic evolution. To date, only two falcon species have been sequenced and neither initially were assembled to the chromosome level. Falcons have atypical avian karyotypes with fewer chromosomes than other birds, presumably brought about by wholesale fusion. To date, however, published chromosome preparations are of poor quality, few chromosomes have been distinguished and standard ideograms have not been made. The purposes of this study were to generate analyzable karyotypes and ideograms of peregrine, saker, and gyr falcons, report on our recent generation of chromosome level sequence assemblies of peregrine and saker falcons, and for the first time, sequence the gyr falcon genome. Finally, we aimed to generate comparative genomic data between all three species and the reference chicken genome. Results revealed a diploid number of 2n = 50 for peregrine falcon and 2n = 52 for saker and gyr through high quality banded chromosomes. Standard ideograms that are generated here helped to map predicted chromosomal fragments (PCFs) from the genome sequences directly to chromosomes and thus generate chromosome level sequence assemblies for peregrine and saker falcons. Whole genome sequencing was successful in gyr falcon, but read depth and coverage was not sufficient to generate a chromosome level assembly. Nonetheless, comparative genomics revealed no differences in genome organization between gyr and saker falcons. When compared to peregrine falcon, saker/gyr differed by one interchromosomal and seven intrachromosomal rearrangements (a fusion plus seven inversions), whereas peregrine and saker/gyr differ from the reference chicken genome by 14/13 fusions (11 microchromosomal) and six fissions. The chromosomal differences between the species could potentially provide the basis of a screening test for hybrid animals.
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Fowler, Katie E., Anjali A. Mandawala, and Darren K. Griffin. "The role of chromosome segregation and nuclear organisation in human subfertility." Biochemical Society Transactions 47, no. 1 (February 7, 2019): 425–32. http://dx.doi.org/10.1042/bst20180231.
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Abstract Spermatogenesis is central to successful sexual reproduction, producing large numbers of haploid motile male gametes. Throughout this process, a series of equational and reductional chromosome segregation precedes radical repackaging of the haploid genome. Faithful chromosome segregation is thus crucial, as is an ordered spatio-temporal ‘dance’ of packing a large amount of chromatin into a very small space. Ergo, when the process goes wrong, this is associated with an improper chromosome number, nuclear position and/or chromatin damage in the sperm head. Generally, screening for overall DNA damage is relatively commonplace in clinics, but aneuploidy assessment is less so and nuclear organisation studies form the basis of academic research. Several studies have focussed on the role of chromosome segregation, nuclear organisation and analysis of sperm morphometry in human subfertility observing significant alterations in some cases, especially of the sex chromosomes. Importantly, sperm DNA damage has been associated with infertility and both extrinsic (e.g. lifestyle) and intrinsic (e.g. reactive oxygen species levels) factors, and while some DNA-strand breaks are repaired, unexpected breaks can cause differential chromatin packaging and further breakage. A ‘healthy’ sperm nucleus (with the right number of chromosomes, nuclear organisation and minimal DNA damage) is thus an essential part of reproduction. The purpose of this review is to summarise state of the art in the fields of sperm aneuploidy assessment, nuclear organisation and DNA damage studies.
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Nasiri, F., F. Mahjoubi, F. Manouchehry, F. Razazian, F. Mortezapour, and M. Rahnama. "Cytogenetic Findings in Mentally Retarded Iranian Patients." Balkan Journal of Medical Genetics 15, no. 2 (December 1, 2012): 29–34. http://dx.doi.org/10.2478/bjmg-2013-0004.
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ABSTRACT We conducted a cytogenetic study on 865 individuals with idiopathic mental retardation (MR) who were admitted to the Cytogenetics Department of the Iran Blood Transfusion Organisation (IBTO) Research Centre, Tehran, Iran; these were performed on blood samples using conventional staining methods. Chromosome anomalies were identified in 205 of the patients (23.6%). The majority were Down’s syndrome cases (n = 138). In 33 males, a positive fragile X anomaly was found .The remainder (n = 34) had other chromosomal abnormalities including structural chromosome aberrations (n = 23), marker chromosomes with an unknown origin (n = 3), sex chromosome aneuploidy (n = 6) and trisomy 18 (n = 2). The contribution of chromosome aberrations to the cause of MR in this group of patients is discussed.
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Sandery, Michael J., John W. Forster, Richard Blunden, and R. Neil Jones. "Identification of a family of repeated sequences on the rye B chromosome." Genome 33, no. 6 (December 1, 1990): 908–13. http://dx.doi.org/10.1139/g90-137.
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A novel family of highly repeated sequences on the B chromosome of rye (Secale cereale) has been identified. The D1100 family has not been detected on the rye A chromosomes and shows little or no homology to any previously described repeat sequence in rye. In addition, different rye species, and different B chromosomes within the same species, show significant heterogeneity in the arrangement of the D1100 sequences. An EcoRI clone of a member of the family has been obtained. These results provide direct evidence for the organisation and nature of the B-chromosome DNA in rye, and they are discussed in relation to the origin and evolution of rye B chromosomes.Key words: B chromosome, Secale cereale, repeated sequences.
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Heslop-Harrison, J. S. Pat, and Trude Schwarzacher. "Organisation of the plant genome in chromosomes." Plant Journal 66, no. 1 (March 28, 2011): 18–33. http://dx.doi.org/10.1111/j.1365-313x.2011.04544.x.
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Cintra, Leonardo Adabo, Thaíssa Boldieri de Souza, Letícia Maria Parteka, Lucas Mesquita Barreto, Luiz Filipe Protasio Pereira, Marcos Letaif Gaeta, Romain Guyot, and André Luís Laforga Vanzela. "An 82 bp tandem repeat family typical of 3′ non-coding end of Gypsy/TAT LTR retrotransposons is conserved in Coffea spp. pericentromeres." Genome 65, no. 3 (March 2022): 137–51. http://dx.doi.org/10.1139/gen-2021-0045.
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Coffea spp. chromosomes are very small and accumulate a variety of repetitive DNA families around the centromeres. However, the proximal regions of Coffea chromosomes remain poorly understood, especially regarding the nature and organisation of the sequences. Taking advantage of the genome sequences of C. arabica (2n = 44), C. canephora, and C. eugenioides (C. arabica progenitors with 2n = 22) and good coverage genome sequencing of dozens of other wild Coffea spp., repetitive DNA sequences were identified, and the genomes were compared to decipher particularities of pericentromeric structures. The searches revealed a short tandem repeat (82 bp length) typical of Gypsy/TAT LTR retrotransposons, named Coffea_sat11. This repeat organises clusters with fragments of other transposable elements, comprising regions of non-coding RNA production. Cytogenomic analyses showed that Coffea_sat11 extends from the pericentromeres towards the middle of the chromosomal arms. This arrangement was observed in the allotetraploid C. arabica chromosomes, as well as in its progenitors. This study improves our understanding of the role of the Gypsy/TAT LTR retrotransposon lineage in the organisation of Coffea pericentromeres, as well as the conservation of Coffea_sat11 within the genus. The relationships between fragments of other transposable elements and the functional aspects of these sequences on the pericentromere chromatin were also evaluated. Highlights: A scattered short tandem repeat, typical of Gypsy/TAT LTR retrotransposons, associated with several fragments of other transposable elements, accumulates in the pericentromeres of Coffea chromosomes. This arrangement is preserved in all clades of the genus and appears to have a strong regulatory role in the organisation of chromatin around centromeres.
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Agashe, Bhavna, Chellapilla Krishna Prasad, and Imran Siddiqi. "Identification and analysis ofDYAD: a gene required for meiotic chromosome organisation and female meiotic progression inArabidopsis." Development 129, no. 16 (August 15, 2002): 3935–43. http://dx.doi.org/10.1242/dev.129.16.3935.
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The dyad mutant of Arabidopsis was previously identified as being defective in female meiosis. We report here the analysis of the DYAD gene. In ovules and anthers DYAD RNA is detected specifically in female and male meiocytes respectively, in premeiotic interphase/meiotic prophase. Analysis of chromosome spreads in female meiocytes showed that in the mutant, chromosomes did not undergo synapsis and formed ten univalents instead of five bivalents. Unlike mutations in AtDMC1 and AtSPO11 which also affect bivalent formation as the univalent chromosomes segregate randomly, the dyad univalents formed an ordered metaphase plate and underwent an equational division. This suggests a requirement for DYAD for chromosome synapsis and centromere configuration in female meiosis. The dyad mutant showed increased and persistent expression of a meiosis-specific marker, pAtDMC1::GUS during female meiosis, indicative of defective meiotic progression. The sequence of the putative protein encoded by DYAD did not reveal strong similarity to other proteins. DYAD is therefore likely to encode a novel protein required for meiotic chromosome organisation and female meiotic progression.
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Hasterok, Robert, Natalia Borowska-Zuchowska, and Ewa Robaszkiewicz. "Cytomolecular Organisation of the Nuclear Genome." International Journal of Molecular Sciences 23, no. 21 (October 27, 2022): 13028. http://dx.doi.org/10.3390/ijms232113028.
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Modern molecular cytogenetics allows many aspects of the nuclear genome structure, function, and evolution to be analysed within the topographic context of mitotic and meiotic chromosomes and interphase nuclei [...]
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Mishra, Sujeet Kumar, Kunhe Li, Simon Brauburger, Arnab Bhattacherjee, Nestor Norio Oiwa, and Dieter W. Heermann. "Superstructure Detection in Nucleosome Distribution Shows Common Pattern within a Chromosome and within the Genome." Life 12, no. 4 (April 6, 2022): 541. http://dx.doi.org/10.3390/life12040541.
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Nucleosome positioning plays an important role in crucial biological processes such as replication, transcription, and gene regulation. It has been widely used to predict the genome’s function and chromatin organisation. So far, the studies of patterns in nucleosome positioning have been limited to transcription start sites, CTCFs binding sites, and some promoter and loci regions. The genome-wide organisational pattern remains unknown. We have developed a theoretical model to coarse-grain nucleosome positioning data in order to obtain patterns in their distribution. Using hierarchical clustering on the auto-correlation function of this coarse-grained nucleosome positioning data, a genome-wide clustering is obtained for Candida albicans. The clustering shows the existence beyond hetero- and eu-chromatin inside the chromosomes. These non-trivial clusterings correspond to different nucleosome distributions and gene densities governing differential gene expression patterns. Moreover, these distribution patterns inside the chromosome appeared to be conserved throughout the genome and within species. The pipeline of the coarse grain nucleosome positioning sequence to identify underlying genomic organisation used in our study is novel, and the classifications obtained are unique and consistent.
Dissertations / Theses on the topic "Organisation des chromosomes"
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Almagro, Sébastien. "Organisation structurale et fonctionnelle des chromosomes." Phd thesis, Université Joseph Fourier (Grenoble), 2003. http://tel.archives-ouvertes.fr/tel-00003099.
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Nous avons utilisé une technique récente de mesure d'élasticité de chromosomes mitotiques assemblés in vitro de Xénope et mis au point une technique de fonctionnalisation par anticorps de micropipettes. Nous avons confirmé que le chromosome mitotique n'était pas un objet homogène. Il est constitué de deux parties bien distinctes : une gaine molle de chromatine et une structure rigide. Nous avons identifié les protéines SMC comme actrices de ces structures rigides. Nous avons aussi montré que l'ADN et les protéines sont nécessaires au maintien de l'organisation des chromosomes alors que l'ARN ne l'est pas. Nous avons aussi étudié le paysage énergétique du chromosome, ce qui n'avait jamais été réalisé sur un objet aussi complexe. Nous proposons un modèle dynamique de formation des chromosomes dans lequel les protéines SMC agissent comme médiatrices de la forme en bâtonnet des chromosomes mitotiques et dans lequel les ions Mg++ et Ca++ jouent le rôle d'agents de
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Donald, Tamzin. "Organisation and expression of plant B chromosomes /." Title page, table of contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phd6758.pdf.
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Fairhead, Cécile. "Proprietes et organisation des chromosomes naturels et artificiels de levure." Paris 6, 1993. http://www.theses.fr/1993PA066089.
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La levure est un eucaryote unicellulaire dont le genome contient toute l'information necessaire a la vie d'une cellule. Ce genome de petite taille est actuellement en cours de sequencage par un ensemble d'equipes internationales. Nous avons participe au sequencage du chromosome iii. L'analyse de la sequence totale du iii confirme que la levure possede un genome compact, sans sequence repetee. Cent quatre-vingt-deux phases ouvertes de lecture de plus de cent codons ont ete revelees sur ce chromosome. La plupart d'entre elles correspondent a des fonctions inconnues jusqu'alors. La grande majorite des genes n'est pas essentielle a la vie de la cellule au laboratoire. La levure fournit des outils pour l'etude des genomes complexes. Nous avons participe a la mise au point de l'utilisation d'une endonuclease tres specifique, fournie par la mitochondrie de levure, utile en cartographie. Par ailleurs, nous avons experimente avec le systeme des chromosomes artificiels de levure, ce qui nous a permis de mettre en evidence un phenomene inattendu de fusion de fragments telomeriques. Enfin, nous avons etudie les mecanismes de reparation des cassures double brin de l'adn chromosomique de levure. Nous avons induit des cassures uniques in vivo, grace a un systeme d'expression nucleaire de l'endonuclease mitochondriale qui coupe des sites introduits artificiellement sur les chromosomes. Nous avons montre que la cassure est reparee en presence d'une copie intacte de la region coupee, par recombinaison homologue. La molecule coupee devient ainsi identique a la copie intacte. S'il n'existe pas de copie intacte de la region coupee, la grande majorite des cellules ne survit pas a l'induction de la cassure. Une faible proportion des cellules survit et repare la coupure par un mecanisme inconnu de religature imparfaite
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Nourse, Jamie. "The structure, organisation and function of dispensable chromosomes in the phytopathogenic fungus Colltotrichum Gloeosporioides /." St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16086.pdf.
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Orsi, Guillaume. "Organisation et intégrité des chromosomes parentaux à la fécondation chez la drosophile." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00848499.
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La reproduction sexuée implique une différentiation extrême des gamètes qui s'accompagne de profonds remaniements des chromosomes parentaux. Au moment de la fécondation, ces chromosomes doivent être rendus compétents pour la formation du premier noyau zygotique. Au cours de ma thèse, j'ai étudié l'importance fonctionnelle de plusieurs voies moléculaires paternelles et maternelles participant à cette étape chez la drosophile. Le complexe HIRA est impliqué dans l'assemblage de nucléosomes dans le pronoyau mâle à la fécondation. J'ai décrit le rôle de HIRA et de son partenaire Yemanucléine-α dans cette voie. J'ai caractérisé plus finement ce complexe en étudiant son rôle somatique dans l'assemblage des nucléosomes et son implication dans la stabilité de l'hétérochromatine, améliorant notre compréhension des besoins biologiques qui conditionnent sa conservation et son évolution. Je me suis aussi intéressé à diverses situations affectant l'intégrité des chromosomes parentaux à la fécondation. (1) J'ai décrit les conséquences catastrophiques pour la méiose femelle de l'expression naturelle d'un transposon à travers l'étude d'un cas de dysgénésie hybride. (2) J'ai contribué à montrer que la protéine K81 est essentielle pour la protection des télomères dans les chromosomes paternels au cours de la spermatogénèse. (3) J'ai participé à caractériser les conséquences pour les chromosomes paternels de l'incompatibilité cytoplasmique induite par la bactérie Wolbachia. Ensemble, ces travaux soulignent les particularités des chromosomes parentaux à la fécondation et aident à cerner l'importance des voies maternelles et paternelles dans leur intégration dans le premier noyau du zygote
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Mercy, Guillaume. "L'organisation 3D des chromosomes synthétiques de levure." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS034/document.
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Le projet international de synthèse des chromosomes de S. cerevisiae (projet Sc2.0) a débuté il y a une dizaine d'années en suivant des principes établis par le Pr. Jef Boeke. Les chromosomes synthétiques ont été conçus pour augmenter la stabilité du génome en supprimant toutes les séquences répétées (ARNt, éléments transposables...), tout en y ajoutant un système d'évolution inductible dépendant du système Cré/LoxP (système SCRaMbLE), permettant de générer rapidement des réarrangements chromosomiques. Bien que le design du projet Sc2.0 soit très conservateur en ce qui concerne le contenu des gènes, la suppression de plusieurs classes de séquences répétées peut affecter l'organisation du génome et potentiellement altérer les fonctions cellulaires. En utilisant la méthode de capture de conformation de chromosome couplée au séquençage de seconde génération (Hi-C), mon objectif a été de caractériser l'organisation 3D des génomes des souches synthétiques et évoluées. À ce jour, huit chromosomes (syn I, II, III, V, VI, IX-R, X et XII) ont été entièrement assemblés séparément. En utilisant les souches contenant un ou plusieurs de ces chromosomes, nous avons pu montrer que leur organisation génomique n'est globalement pas affectée par leur présence. Quelques exceptions subsistent, avec synIII dont les cassettes HML et HMR ont été retirées, et synXII d'où l'ADNr a été déplacé sur un autre chromosome. À ce stade, nous concluons que l'ADN répétitif dispersé ne conduit pas la conformation moyenne globale du génome de S. cerevisiae. Nous avons aussi exploité les cartes de contacts pour identifier les réarrangements dans les souches SCRaMbLEThe international project Sc2.0 started 10 years ago by the Pr. Jef Boeke aims to build a fully synthetic genome of S. cerevisiae which increases the genome stability by removing all repeated sequences (tRNA, transposable elements, etc.), and implements SCRaMbLE (for Synthetic Chromosome Rearrangement and Modification by LoxP-mediated Evolution), an inducible, high-throughput chromosome rearrangement system. This design is highly conservative with respect to gene content, the deletion of several classes of repeated sequences and the introduction of thousands of designer changes. However, it may affect genome organization and potentially alter cellular functions. To determine wether those modifications affected the three-dimensional conformation of synthetic chromosmes, we investigated it using chromosomes conformation capture coupled to second generation sequencing method (Hi-C). Currently, eight synthetic chromosomes (synI, synII, synIII, synV, synVI, synIX-R, synX et synXII) have been fully assembled. Using these strains we observed that the large-scale genomic organization is globally unaffected by the presence of synthetic chromosome(s). Two exceptions are synIII, which lacks the silent mating-type cassettes, and synXII, specifically when the ribosomal DNA is moved to another chromosome. We also exploited the contact maps to detect rearrangements induced in these SCRaMbLE strains
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Mercy, Guillaume. "L'organisation 3D des chromosomes synthétiques de levure." Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS034.pdf.
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Le projet international de synthèse des chromosomes de S. cerevisiae (projet Sc2.0) a débuté il y a une dizaine d'années en suivant des principes établis par le Pr. Jef Boeke. Les chromosomes synthétiques ont été conçus pour augmenter la stabilité du génome en supprimant toutes les séquences répétées (ARNt, éléments transposables...), tout en y ajoutant un système d'évolution inductible dépendant du système Cré/LoxP (système SCRaMbLE), permettant de générer rapidement des réarrangements chromosomiques. Bien que le design du projet Sc2.0 soit très conservateur en ce qui concerne le contenu des gènes, la suppression de plusieurs classes de séquences répétées peut affecter l'organisation du génome et potentiellement altérer les fonctions cellulaires. En utilisant la méthode de capture de conformation de chromosome couplée au séquençage de seconde génération (Hi-C), mon objectif a été de caractériser l'organisation 3D des génomes des souches synthétiques et évoluées. À ce jour, huit chromosomes (syn I, II, III, V, VI, IX-R, X et XII) ont été entièrement assemblés séparément. En utilisant les souches contenant un ou plusieurs de ces chromosomes, nous avons pu montrer que leur organisation génomique n'est globalement pas affectée par leur présence. Quelques exceptions subsistent, avec synIII dont les cassettes HML et HMR ont été retirées, et synXII d'où l'ADNr a été déplacé sur un autre chromosome. À ce stade, nous concluons que l'ADN répétitif dispersé ne conduit pas la conformation moyenne globale du génome de S. cerevisiae. Nous avons aussi exploité les cartes de contacts pour identifier les réarrangements dans les souches SCRaMbLEThe international project Sc2.0 started 10 years ago by the Pr. Jef Boeke aims to build a fully synthetic genome of S. cerevisiae which increases the genome stability by removing all repeated sequences (tRNA, transposable elements, etc.), and implements SCRaMbLE (for Synthetic Chromosome Rearrangement and Modification by LoxP-mediated Evolution), an inducible, high-throughput chromosome rearrangement system. This design is highly conservative with respect to gene content, the deletion of several classes of repeated sequences and the introduction of thousands of designer changes. However, it may affect genome organization and potentially alter cellular functions. To determine wether those modifications affected the three-dimensional conformation of synthetic chromosmes, we investigated it using chromosomes conformation capture coupled to second generation sequencing method (Hi-C). Currently, eight synthetic chromosomes (synI, synII, synIII, synV, synVI, synIX-R, synX et synXII) have been fully assembled. Using these strains we observed that the large-scale genomic organization is globally unaffected by the presence of synthetic chromosome(s). Two exceptions are synIII, which lacks the silent mating-type cassettes, and synXII, specifically when the ribosomal DNA is moved to another chromosome. We also exploited the contact maps to detect rearrangements induced in these SCRaMbLE strains
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Brun, Christine. "Organisation en boucles de la molécule d'ADN et réplication : tude de la région 14B-15B du chromosome X et de l'unité des gènes ribosomiques de Drosophila melanogaster." Aix-Marseille 2, 1992. http://www.theses.fr/1992AIX22017.
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La molecule d'adn, constitutive du chromosome eucaryote, est organisee en boucles dont les bases sont ancrees dans un reseau proteique interne nomme scaffold. L'implication des sites d'attachement de la molecule d'adn au scaffold (=sar) dans les mecanismes de replication a ete etudiee dans deux regions distinctes du genome de la drosophile: la region 14b-15b du chromosome x, mesurant 800 kb, qui a ete clonee dans le laboratoire et dont l'organisation en boucles a ete determinee lors d'une etude anterieure, et l'unite des genes codant pour les arns ribosomiques. Dans une premiere etape, l'activite de replication autonome (=ars) de fragments de restriction representatifs de la region 14b-15b a ete testee par transformation heterologue de levure. 27 fragments manifestent une activite ars. 25 d'entre eux sont des sars. Il existe donc une correlation entre les deux types d'activites: une sous-classe de sars de drosophile est impliquee dans les mecanismes de replication extrachromosomique chez la levure. De plus, l'association au scaffold est conservee entre les deux especes: lors d'un test de re-association in vitro, 61% des sars testes sont capables de s'associer a des scaffolds de levure. Dans une deuxieme etape, l'existence d'une relation entre sites d'attachement, sequences ars dans la levure et origines de replication chromosomiques a ete abordee. Pour cela, l'organisation en boucles de l'unite repetee des genes ribosomiques a ete determinee. Trois sars ont ete identifies a l'interieur des trois espaceurs presents dans l'unite. Ils definissent trois boucles d'adn contenant la region codant pour l'arn 18s, une partie de la region codant pour l'arn 28s et une region entourant le site +1 de transcription, respectivement. Ces 3 sars de drosophile sont egalement capables de s'associer a des scaffolds de levure. Trois regions de l'unite sont impliquees dans les mecanismes de replication extrachromosomique chez la levure. Elles correspondent aux regions en interaction avec le scaffold. De plus, la technique d'electrophorese bidimensionnelle neutre/neutre a permis de localiser une origine de replication chromosomique dans un fragment d'adn couvrant deux des espaceurs. Ces resultats montrent donc qu'au moins dans un cas, une proximite topologique existe entre des sequences impliquees dans l'association de la molecule d'adn au scaffold, dans la replication extrachromosomique chez la levure et dans l'initiation de la replication chromosomique. Cela suggere une relation fonctionnelle etroite entre ces trois types de sequences
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Augui, Sandrine. "Interactions chromosomiques et inactivation du chromosome X : éléments génétiques et mécanismes impliqués dans la reconnaissance du nombre de chromosomes X et dans la coordination des centres d'inactivation." Paris 11, 2009. http://www.theses.fr/2009PA112373.
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Le locus Xic contrôle l'initiation de l'inactivation du chromosome X. Il est nécessaire à la reconnaissance du nombre de chromosomes X (Sensing) et au déclenchement de l'expression monoallélique de Xist. Nous avons étudié la dynamique nucléaire des Xics au cours de la mise en place de l'inactivation dans les cellules ES. Nous avons montré que lors de l'initiation de l'inactivation, les deux Xics interagissent physiquement. Cet appariement transitoire permettrait la coordination des Xics afin de ne mettre en place l'inactivation qu'en présence de deux chromosomes X et au niveau d'un seul. Nous avons montré que cet appariement impliquait une région du Xic nommée Xpr pour "X-pairing region". Des expériences de transgénèse montrent que cette région est capable d'induire la trans-interaction des Xics de façon autonome et peut aussi induire l'activation du gène Xist endogène. Xpr serait ainsi le premier activateur en trans de Xist identifié à ce jour. La présence ectopique de Xpr semble en outre associée à une instabilité génétique dans les cellules ES. Notre modèle propose que l'appariement homologue des régions Xpr serait impliqué dans la coordination des Xics en ne permettant l'activation de Xist qu'en présence de plusieurs chromosomes X, et au niveau du nombre de X nécessaires pour rétablir la compensation de dose. En l'occurrence, des lignées males double transgéniques pour Xpr et Xist/Tsix semblent mettre en place au cours de leur différenciation un processus aléatoire d'inactivation, comparable à celui observé dans des lignées femelles, suggérant que Xpr+Xist/Tsix récapitulerait l'ensemble des fonctions du Xic et représenterait donc la région minimum du XicIn mammals, dosage compensation is achieved by the inactivation of one of the two X-chromosome during early development in females. X inactivation process is controlled by a complex locus, the X-inactivation centre (Xic), which includes the Xist gene and its antisense transcription unit Tsix/Xite. The Xic senses X chromosome number and initiates inactivation by triggering mono-allelic up-regulation of Xist RNA, and reciprocally, down-regulation of Tsix from one of the two X chromosomes in females. However, the mechanisms underlying sensing and reciprocal Xist/Tsix regulation remain obscure. We recently showed that a previously untested segment of the Xic, lying several hundred kilobases upstream of Xist and enriched in histone H3K27me3 and H3K9me2 marks, brings the two Xic's together prior to the onset of X inactivation (Augui et al, Science 318:1362, 2007). This X-pairing-region (Xpr) can autonomously drive Xic trans-interactions even as an ectopic single copy transgene. Furthermore its presence in male ES cells is selected against, suggesting that it may have a role in triggering Xist up regulation. We proposed that the pairwise interactions driven by this novel X-pairing-region (Xpr) of the Xic might enable a cell to sense that more than one X-chromosome is present in an XX cell, by activating biallelic Xist expression. Furthermore we believe that Xpr pairing then facilitates association between the Tsix/Xite regions, thus rendering biallelic Xist expression monoallelic. Finally, we think that Xpr could be the missing functional region of the Xic since Xpr + Xist/Tsix transgenes seem to recapitulate all Xic function in a male cell line
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Toulouze, Mathias. "Analyse de la dynamique des chromosomes chez Saccharomyces cerevisiae." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC149.
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La difficulté et la nécessité d'étudier l'organisation dynamique du génome ont poussé ces dernières années les expérimentateurs et les théoriciens à collaborer au développement de modèles théoriques de l'architecture chromosomique. Notre travail s’inscrit dans cet effort. En collaboration avec David Holcman et Assaf Amitaï (ENS Paris), nous avons développé une nouvelle méthode d'analyse de la mobilité de sites chromosomiques marqués avec des protéines fluorescentes. Notre analyse a permis de comparer la mobilité des différents sites du génome afin de comprendre comment l’organisation du noyau influe sur la mobilité de la chromatine, puis dans un second temps nos résultats ont permis d’établir un lien entre les mécanismes de réparation de l’ADN et la mobilité. Il a déjà été prouvé récemment (K. Bloom, 2013) que la mobilité des chromosomes est limitée par leur ancrage au SPB via leur centromère, mais l’étude de l'impact de l’ancrage télomérique sur la mobilité des chromosomes méritait d’être approfondi. Contrairement à ce qui est communément admis, nos résultats ont montré que les télomères ne sont pas fortement ancrés à la membrane nucléaire, de plus il existe une grande variabilité de leur mobilité cellule à cellule. Dans la plupart des cellules, l'interaction télomérique avec la membrane nucléaire est en effet suffisamment forte pour modifier la localisation des locus sub-télomériques mais trop faible pour impacter sa mobilité. Nos résultats ont également montré que les loci sub-télomériques ont une mobilité supérieure à celle des locus situés au milieu du bras chromosomique. Dans les cellules mutantes, la perte de l'intégrité du chromosome lors de l'induction d'une CDB entraîne l'apparition d’extrémités libres sur la chromatine. De manière similaire aux locus sub-télomériques, les extrémités libres des CDB présentent une mobilité plus élevée que les CDB du chromosome dont l'intégrité est préservée, ceci qui pouvant s'expliquer par un degré de liberté de mouvement supérieur des extrémités de la chromatine. Les cassures double-brin de l’ADN sont parmi les lésions les plus toxiques. La non- réparation ou une mauvaise réparation de ces cassures conduit à la mort cellulaire ou à des réarrangements chromosomiques qui sont à l’origine du développement de cancers chez l’homme. Lorsque que la cassure de l’ADN se produit la molécule d’ADN porteuse de l’information génétique est rompue sur les deux brins mais les deux extrémités de la cassure sont maintenues ensemble ce qui préserve l’intégrité du chromosome. En effet l’observation des extrémités de la cassure par microscopie grâce à des tags fluorescents situés de chaque côté de la cassure montre que celles-ci sont maintenues à proximité l’une de l’autre. Il existe donc un ou plusieurs mécanismes permettant à la cellule de préserver l’intégrité du chromosome. Des travaux précédents ont identifié le complexe MRX comme étant l’un des acteurs essentiels de ce mécanisme. Nos travaux ont permis d’identifier une seconde voie, complémentaire de MRX permettant d’assurer le maintien de l’intégrité chromosomique. Nous avons aussi pu observer que nos observations statiques concernant la proportion de cellules présentant des extrémités séparées était en réalité à l’échelle de la cellule le résultat d'un processus dynamique, les extrémités des chromosomes pouvant au cours du temps plusieurs fois se retrouver puis se séparer à nouveau. Afin de mieux comprendre les mécanismes de cohésion entre extrémités, nous avons pensé qu'il était essentiel de comprendre l'impact du recrutement des cohésines sur l'organisation 3D de la chromatine autour de la cassure. En effet, le recrutement de cohésines sur des dizaines de kilobases autour de la rupture est susceptible de générer l'assemblage d'une grande structure capable de modifier l'organisation 3D du chromosome à grande échelleThe difficulty and the need to study the dynamic organization of the genome have pushed in recent years, experimenters and theorists to collaborate in the development of theoretical models of chromosomal architecture. Our work is a part of this effort. In collaboration with David Holcman and Assaf Amitaï (ENS Paris), we developped a new method of data analysis for the study of chromosomal sites tagged with fluorescent proteins. This new method allows us to extract from miscroscopy analysis a parameter named Kc characterizing constraints that restrict the mobility of the chromosomal locus. This new analysis was used to compare the mobility of different sites in the genome in order to understand how organization of the nucleus impacts chromatin mobility with the final aim of understanding the impact of this mobility on the regulation of DNA repair mechanisms. It was already proven recently (K. Bloom, 2013) that mobility of chromosomes is constrained by their anchoring to SPB by their centromeres, but little was known about the impact of telomeric sequences to nuclear membrane on chromosome mobility. Contrary to what is commonly accepted, our results showed that telomeres are not strongly anchored to the nuclear membrane. Within a cell population, it exists a high variability in telomere mobility, indeed most of the cells the telomeric interaction with the nuclear membrane is indeed strong enough to change the location of sub-telomeric loci but too weak to impact its mobility. Our results also showed that sub-telomeric loci have a higher mobility than loci located in the middle of the same chromosome arm. In mutant cells the loss of chromosom integrity upon the induction of a double-strand break leads to the apparition chromatin free extremities. Similarly to sub-telomerics loci, DSBs free extremities exhibit a higher mobility than DSBs in chromosome with a preserved integrity. In summary our study has shown that free ends of a chromatin fiber have a higher mobility than other monomers in the chain. This higher mobility is due to the higher level of freedom that chromatin extremities have. When DNA double strand break (DSB) is generated, the chromosome ends should become physically totally dissociated from one to another, making ensuing repair difficult. To overcome this dramatic event, the DNA damage response (DDR) takes in charge the implementation of a protein bridge that holds the two chromosome ends together and so preserve its integrity. In S. cerevisiae the MRX complex was already known for playing critical functions in early DSB extremities tethering. Several studies showed that a single DSB induces the formation of a ≈100 kb cohesin domain around the lesion. Our study suggests the late role played by cohesins in the emergence of an intra-chromosomal cohesive structure capable to maintain chromosomal integrity. The way of DSB extremities cohesion is established, is consistent with what is published on the recruitment of cohesins at DSBs. Our study also highlight the dynamical behavior of DSB extremities at the cell scale. Indeed once DSB extremities are separated, they alternate during several hours between a tethered and a separated state. We also analysed the impact of cohesins recruitment at DSBs at the chromosome scale. Our results establish a positive correlation between the level of cohesins loaded on the chromosome and the level of folding of the chromatin fiber. The analysis of the chronology of events leading to the preservation of chromosomal integrity upon DSB suggests that chromatin has an intrinsic property (not related to DNA damage response) preserving its integrity despite the apparition of DSBs. This property could potentially be due to short-range inter-nucleosomal interactions or to the presence of secondary structures formed by cohesines in the interphase genome. All these hypothesis should be further tested experimentally
Books on the topic "Organisation des chromosomes"
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Wieser, Bernhard. Assessing life: On the organisation of genetic testing. München: Profil, 2010.
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Scott, G. B. Transcriptional organisation and regulation of the chromosomal replication origin region of streptomyces coelicolor A3(2). Manchester: UMIST, 1995.
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Richard, Claudia. Die Amplifikation der Nucleolus-Organisator-Regionen (NOR) der akrozentrischen Chromosomen: Ihre Bedeutung für die genetische Beratung. [s.l.]: [s.n.], 1995.
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Books, Cambridge Stanford, and John Kaisermann. Organisation des Chromosomes Humains. Independently Published, 2019.
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Books, Cambridge Stanford, and John Kaisermann. Organisation Menschlicher Chromosomen. Independently Published, 2019.
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Books, Cambridge Stanford, and John Kaisermann. Organisatie Van Menselijke Chromosomen. Independently Published, 2019.
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Lübeck, Medizinische Universität zu, ed. Transkription, Organisation und Evolution amplifizierter "long-range repeat" Sequenzen aus dem Chromosom 1 der Hausmaus (Mus musculus). 1992.
Find full textBook chapters on the topic "Organisation des chromosomes"
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de Jong, J. H., X. B. Zhong, P. F. Fransz, J. Wennekes-van Eden, E. Jacobsen, and P. Zabel. "High resolution FISH reveals the molecular and chromosomal organisation of repetitive sequences of individual tomato chromosomes." In Chromosomes Today, 267–75. Basel: Birkhäuser Basel, 2000. http://dx.doi.org/10.1007/978-3-0348-8484-6_20.
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Prakash, Kirti. "Periodic and Symmetric Organisation of Meiotic Chromosomes." In Springer Theses, 105–33. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-52183-1_4.
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Smith-Keary, Peter. "Chromosome organisation." In Molecular Genetics, 31–46. London: Macmillan Education UK, 1991. http://dx.doi.org/10.1007/978-1-349-11732-1_3.
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Bridger, Joanna M., Rita Torres Pereira, Cristina Pina, Sabrina Tosi, and Annabelle Lewis. "Alterations to Genome Organisation in Stem Cells, Their Differentiation and Associated Diseases." In Nuclear, Chromosomal, and Genomic Architecture in Biology and Medicine, 71–102. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-06573-6_3.
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Podgornaya, Olga, Ekaterina Gavrilova, Vera Stephanova, Sergey Demin, and Aleksey Komissarov. "Large Tandem Repeats Make up the Chromosome Bar Code." In Organisation of Chromosomes, 1–30. Elsevier, 2013. http://dx.doi.org/10.1016/b978-0-12-410523-2.00001-8.
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Enukashvily, Natella I., and Nikita V. Ponomartsev. "Mammalian Satellite DNA." In Organisation of Chromosomes, 31–65. Elsevier, 2013. http://dx.doi.org/10.1016/b978-0-12-410523-2.00002-x.
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Feinauer, Christoph J., Andreas Hofmann, Sebastian Goldt, Lei Liu, Gabriell Máté, and Dieter W. Heermann. "Zinc Finger Proteins and the 3D Organization of Chromosomes." In Organisation of Chromosomes, 67–117. Elsevier, 2013. http://dx.doi.org/10.1016/b978-0-12-410523-2.00003-1.
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Ramaswamy, Amutha, and Ilya Ioshikhes. "Dynamics of Modeled Oligonucleosomes and the Role of Histone Variant Proteins in Nucleosome Organization." In Organisation of Chromosomes, 119–49. Elsevier, 2013. http://dx.doi.org/10.1016/b978-0-12-410523-2.00004-3.
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Silván, Unai, Brigitte M. Jockusch, and Cora-Ann Schoenenberger. "Unconventional Actin Configurations Step into the Limelight." In Organisation of Chromosomes, 151–77. Elsevier, 2013. http://dx.doi.org/10.1016/b978-0-12-410523-2.00005-5.
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Vagnarelli, Paola. "Chromatin Reorganization Through Mitosis." In Organisation of Chromosomes, 179–224. Elsevier, 2013. http://dx.doi.org/10.1016/b978-0-12-410523-2.00006-7.
Full textConference papers on the topic "Organisation des chromosomes"
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Menon, Shankar, Luis Valencia, and Lucien Teunckens. "The Nuclear Decommissioner and the Regulation of Low Dose Radiation." In ASME 2003 9th International Conference on Radioactive Waste Management and Environmental Remediation. ASMEDC, 2003. http://dx.doi.org/10.1115/icem2003-4665.
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The management of the large quantities of very low level radioactive material that arise during the decommissioning of the increasing numbers of nuclear power stations reaching the end of their commercially useful lives, has become a major subject of discussion. This has very significant economic implications for the nuclear decommissioner. Much larger quantities — 2–3 orders of magnitude larger — of material, radiologically similar to the candidate material for recycling from the nuclear industry, arise in non-nuclear industries like coal, fertiliser, oil and gas, mining, etc. In such industries, naturally occurring radioactivity is artificially concentrated in products, by-products or waste to form TENORM (Technologically Enhanced Naturally Occurring Radioactive Material). It is only in the last decade that the international community has become aware of the prevalence of TENORM, specially the activity levels and quantities arising in so many non-nuclear industries. The first reaction of international organisations seems to have been to propose different standards for the nuclear and non-nuclear industries, with very stringent release criteria for radioactive material from the regulated nuclear industry and up to thirty to a hundred times more liberal criteria for the release/exemption of TENORM from the as yet unregulated non-nuclear industries. The radiological effects of these TENORM releases have recently been dramatically highlighted by the Marina II study, which showed that over 90% of the total exposures of the European population from discharges into the North European marine waters are from radioactive discharges from non-nuclear industries. The results of an international project to validate, by actual measurement, dose calculation codes RESRAD-RECYCLE (USA) and CERISE (France) for recycling, have indicated an overestimation of doses by the codes by an order of magnitude. For the nuclear decommissioner and other producers of large volumes of slightly radioactively contaminated material, clearance levels determined on the basis of such a degree of conservatism in calculations can lead to huge volumes of material unnecessarily being condemned to burial as radioactive waste. Earlier estimates of the quantitative risk levels of exposure to ionising radiation have almost exclusively been based on doses taken by exposed populations of Hiroshima and Nagasaki (ICRP 60). The populations studied have been exposed to over 200 mSv at a dose rate of 6 Sv/s. The effects of such high dose/dose-rate exposure are being used as the basis for risk judgment at doses/dose-rates lower by a factor 1012–1015. The validity of such an extrapolation in risk judgement is an area of prime interest for discussion. In this connection, an interesting development, for both the nuclear and non-nuclear industries, is the increased scientific scrutiny that the populations of naturally high background dose level areas of the world are being subject to. Preliminary biological studies have indicated that the inhabitants of such areas, exposed to many times the permitted occupational doses for nuclear workers, have not shown any differences in cancer mortality, life expectancy, chromosome aberrations or immune function, in comparison with those living in normal background areas. The paper discusses these and other strategic issues regarding the management of redundant low radiation material from both the nuclear and non-nuclear industries, underlining the need for consistency in regulatory treatment.