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Recombination frequency, chiasma counts and the process of crossing-overNilsson, Nils-Otto. January 1994 (has links)
Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.
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Recombination frequency, chiasma counts and the process of crossing-overNilsson, Nils-Otto. January 1994 (has links)
Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.
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Induced mitotic recombination in Aspergillus strains differing in sensitivity to ultraviolet light.Shanfield, Bernice G. January 1968 (has links)
No description available.
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The effect of X chromosome inversions on crossing-over in the third chromosome of Drosophila melanogaster. --.Fraser, Frank Clarke. January 1941 (has links)
No description available.
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Induced mitotic recombination in Aspergillus strains differing in sensitivity to ultraviolet light.Shanfield, Bernice G. January 1968 (has links)
No description available.
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Caractérisation de variations naturelles de fréquence de crossovers chez le colza (Brassica napus) / Caracterization of natural variation of crossover rate in Oilseed rape (Brassica napus)Grandont, Laurie 09 March 2012 (has links)
La méiose est un processus fondamental qui conditionne la formation de gamètes et assure la stabilité des génomes tout en générant de la diversité par brassage génétique. La régularité méiotique nécessite la formation de crossing-overs (CO) exclusivement entre chromosomes homologues. Cette condition est plus difficile à remplir chez les espèces allopolyploïdes qui présentent plusieurs jeux de chromosomes toujours susceptibles de recombiner ensemble. Bien que la polyploïdie soit omniprésente chez les plantes, on connait peu de choses sur le déroulement de la méiose chez ces espèces. Au cours de ma thèse, je suis intéressée à l’effet de la polyploïdie sur la formation et sur la fréquence de CO en utilisant le colza (Brassica napus, AACC, 2n=38) comme modèle d’étude. J’ai notamment cherché à comprendre : (1) quel est l’effet du niveau de ploïdie sur la fréquence de crossovers, et (2) l’origine des variations de COs observées chez les plantes allohaploïdes (AC) produites à partir de différentes variétés de colza, en utilisant une palette d’approches cytologiques et cytogénétiques. Mes travaux ont permis de montrer que le niveau de ploïdie induit une augmentation de la fréquence de crossovers, et que cette augmentation est plus importante dans un contexte triploïde que tétraploïde. J’ai ainsi montré que la fréquence de CO augmente progressivement du diploïde (1,6 CO/bivalent) vers le tétraploïde (2 CO/bivalents) et quelle est maximale chez le triploïde (2,8 CO/bivalent). En ce qui concerne la deuxième question, j’ai montré que la différence entre les allohaploïdes de colzas apparaît tardivement au cours de la méiose. Elle semble être liée à une capacité différente à former des CO en fonction de la variété utilisée pour produire ces allohaploïdes et non pas à une différence dans la reconnaissance de l’homologie. Un de mes résultats original est que la protéine HEI10, impliquée dans la voie de formation des CO interférents, présente une dynamique différente entre les deux variétés, que ce soit à l’état euploïde (AACC) qu’allohaploïde (AC).Mes résultats conduisent à s’interroger sur la relation entre (i) la régulation du nombre de CO formés entre chromosomes homologues et (ii) la suppression des CO entre chromosomes non homologues chez les espèces allopolyploïdes. / Meiosis is a fundamental process required to produce gametes, ensure genome stability and generate diversity within species by creating new chromosome/allele combinations. For all these outcomes the exclusive formation of crossovers (CO) between homologous chromosomes is required. This condition is more difficult to fulfil in allopolyploid species that have more than two sets of chromosomes still able to recombine together. Although polyploidy has been particularly prevalent in plants, little is known about meiosis in polyploids. During my thesis I have analyzed the effect of polyploidy on CO formation and frequency, using oilseed rape (Brassica napus, AACC, 2n=38) as model. My work aimed to investigate (i) the effect of ploidy level on the rate of meiotic COs and (ii) the causes for the observed difference in CO rate between allohaploid plants (AC) produced from different B. napus varieties. To address these questions, I have combined a series of cytological, immunocytological and cytogenetical analyses.My work first indicates that polyploidization leads to increase CO frequency. I showed that the number of COs progressively increases from the diploid (1,6 CO/bivalent) to the tetraploid (2 CO/bivalent) and is maximal in the triploid (2,8 CO/bivalent). In the second part, I have shown that the difference of meiotic behaviors between B. napus allohaploids appears at a late stage of meiosis. This difference seems to be due to a difference in the propensity to form CO between the two varieties rather than a difference in the stringency of homology recognition. This difference could be related to the difference in the pattern and/or chronology of HEI10 (a key protein involved in the interfering CO pathway) signals along chromosomes during prophase I in both euploids (AACC) and allohaploids (AC).My results thus puts under the spotlight the link that may exist between (i) the regulation of CO rate between homologous chromosomes and (ii) the suppression of COs between non-homologous chromosomes in polyploid species.
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Comparative study of inter and intralocus recombination in DrosophilaScholefield, Dorothy Jane Stuart January 1965 (has links)
The effect of different treatments on crossing over between and within genes at the tip of the X chromosome of Drosophila melanogaster was studied to determine whether exchange in the two regions occurs by different mechanisms. In response to autosomal inversions, ɣ -radiation, and heat shock, crossing over of both types was altered in the same direction and to a comparable extent. This would be expected if there were only one crossover mechanism involved. There was some difference in response of interlocus and intralocus crossing over after mitomycin C injection but, since the effect on interlocus crossing over in two separate regions was not consistent, the significance of this result is questionable. Although double crossing over involving the two interlocus regions was very rare doubles involving an inter and an intralocus region were recovered. The association of exchanges within a gene with a crossover between genes might indicate that there are two noninterfering mechanisms, or that multiple exchanges occur in short effectively paired regions. A further experiment designed to detect switch regions is outlined. / Science, Faculty of / Zoology, Department of / Graduate
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Chromosome pairing and the isolation of "2-chromosome, double interchanges" in barley, Hordeum vulgare L.Fastnaught, Christine Elizabeth January 1980 (has links)
No description available.
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Influence of chromosomal aberrations on meiotic non-disjunction in Aspergillus.Pollard, D. Russell (Donald Russell). January 1966 (has links)
Studies on chromosomal segregation in higher organisms have established a definite relationship between crossing-over and nondisjunction -- the two appear to be inversely correlated. Most of the experiments performed involve segregation from inversion and translocation heterozygotes. [...]
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Influence of chromosomal aberrations on meiotic non-disjunction in AspergillusPollard, D. Russell (Donald Russell) January 1966 (has links)
No description available.
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