Littérature scientifique sur le sujet « Mutation rate evolution »
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Articles de revues sur le sujet "Mutation rate evolution":
1
Trindade, Sandra, Lilia Perfeito et Isabel Gordo. « Rate and effects of spontaneous mutations that affect fitness in mutator Escherichia coli ». Philosophical Transactions of the Royal Society B : Biological Sciences 365, no 1544 (27 avril 2010) : 1177–86. http://dx.doi.org/10.1098/rstb.2009.0287.
Résumé :
Knowledge of the mutational parameters that affect the evolution of organisms is of key importance in understanding the evolution of several characteristics of many natural populations, including recombination and mutation rates. In this study, we estimated the rate and mean effect of spontaneous mutations that affect fitness in a mutator strain of Escherichia coli and review some of the estimation methods associated with mutation accumulation (MA) experiments. We performed an MA experiment where we followed the evolution of 50 independent mutator lines that were subjected to repeated bottlenecks of a single individual for approximately 1150 generations. From the decline in mean fitness and the increase in variance between lines, we estimated a minimum mutation rate to deleterious mutations of 0.005 (±0.001 with 95% confidence) and a maximum mean fitness effect per deleterious mutation of 0.03 (±0.01 with 95% confidence). We also show that any beneficial mutations that occur during the MA experiment have a small effect on the estimate of the rate and effect of deleterious mutations, unless their rate is extremely large. Extrapolating our results to the wild-type mutation rate, we find that our estimate of the mutational effects is slightly larger and the inferred deleterious mutation rate slightly lower than previous estimates obtained for non-mutator E. coli .
2
Sherer, Nicholas A., et Thomas E. Kuhlman. « Escherichia coli with a Tunable Point Mutation Rate for Evolution Experiments ». G3: ; Genes|Genomes|Genetics 10, no 8 (5 juin 2020) : 2671–81. http://dx.doi.org/10.1534/g3.120.401124.
Résumé :
The mutation rate and mutations’ effects on fitness are crucial to evolution. Mutation rates are under selection due to linkage between mutation rate modifiers and mutations’ effects on fitness. The linkage between a higher mutation rate and more beneficial mutations selects for higher mutation rates, while the linkage between a higher mutation rate and more deleterious mutations selects for lower mutation rates. The net direction of selection on mutations rates depends on the fitness landscape, and a great deal of work has elucidated the fitness landscapes of mutations. However, tests of the effect of varying a mutation rate on evolution in a single organism in a single environment have been difficult. This has been studied using strains of antimutators and mutators, but these strains may differ in additional ways and typically do not allow for continuous variation of the mutation rate. To help investigate the effects of the mutation rate on evolution, we have genetically engineered a strain of Escherichia coli with a point mutation rate that can be smoothly varied over two orders of magnitude. We did this by engineering a strain with inducible control of the mismatch repair proteins MutH and MutL. We used this strain in an approximately 350 generation evolution experiment with controlled variation of the mutation rate. We confirmed the construct and the mutation rate were stable over this time. Sequencing evolved strains revealed a higher number of single nucleotide polymorphisms at higher mutations rates, likely due to either the beneficial effects of these mutations or their linkage to beneficial mutations.
3
Stephan, Wolfgang. « The Rate of Compensatory Evolution ». Genetics 144, no 1 (1 septembre 1996) : 419–26. http://dx.doi.org/10.1093/genetics/144.1.419.
Résumé :
Abstract A two-locus model is presented to analyze the evolution of compensatory mutations occurring in stems of RNA secondary structures. Single mutations are assumed to be deleterious but harmless (neutral) in appropriate combinations. In proceeding under mutation pressure, natural selection and genetic drift from one fitness peak to another one, a population must therefore pass through a valley of intermediate deleterious states of individual fitness. The expected time for this transition is calculated using diffusion theory. The rate of compensatory evolution, kc, is then defined as the inverse of the expected transition time. When selection against deleterious single mutations is strong, kc, depends on the recombination fraction r between the two loci. Recombination generally reduces the rate of compensatory evolution because it breaks up favorable combinations of double mutants. For complete linkage, kc, is given by the rate at which favorable combinations of double mutantS are produced by compensatory mutation. For r > 0, kc, decreases exponentially with r. In contrast, kc, becomes independent of r for weak selection. We discuss the dynamics of evolutionary substitutions of compensatory mutants in relation to Wright'S shifting balance theory of evolution and use our results to analyze the substitution process in helices of mRNA secondary structures.
4
Sniegowski, Paul. « Evolution : Setting the mutation rate ». Current Biology 7, no 8 (août 1997) : R487—R488. http://dx.doi.org/10.1016/s0960-9822(06)00244-2.
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Lynch, Michael. « Evolution of the mutation rate ». Trends in Genetics 26, no 8 (août 2010) : 345–52. http://dx.doi.org/10.1016/j.tig.2010.05.003.
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Schoen, Daniel J., et Stewart T. Schultz. « Somatic Mutation and Evolution in Plants ». Annual Review of Ecology, Evolution, and Systematics 50, no 1 (2 novembre 2019) : 49–73. http://dx.doi.org/10.1146/annurev-ecolsys-110218-024955.
Résumé :
Somatic mutations are common in plants, and they may accumulate and be passed on to gametes. The determinants of somatic mutation accumulation include the intraorganismal selective effect of mutations, the number of cell divisions that separate the zygote from the formation of gametes, and shoot apical meristem structure and branching. Somatic mutations can promote the evolution of diploidy, polyploidy, sexual recombination, outcrossing, clonality, and separate sexes, and they may contribute genetic variability in many other traits. The amplification of beneficial mutations via intraorganismal selection may relax selection to reduce the genomic mutation rate or to protect the germline in plants. The total rate of somatic mutation, the distribution of selective effects and fates in the plant body, and the degree to which the germline is sheltered from somatic mutations are still poorly understood. Our knowledge can be improved through empirical estimates of mutation rates and effects on cell lineages and whole organisms, such as estimates of the reduction in fitness of progeny produced by within- versus between-flower crosses on the same plant, mutation coalescent studies within the canopy, and incorporation of somatic mutation into theoretical models of plant evolutionary genetics.
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Krasovec, Marc, Rosalind E. M. Rickaby et Dmitry A. Filatov. « Evolution of Mutation Rate in Astronomically Large Phytoplankton Populations ». Genome Biology and Evolution 12, no 7 (1 juillet 2020) : 1051–59. http://dx.doi.org/10.1093/gbe/evaa131.
Résumé :
Abstract Genetic diversity is expected to be proportional to population size, yet, there is a well-known, but unexplained lack of genetic diversity in large populations—the “Lewontin’s paradox.” Larger populations are expected to evolve lower mutation rates, which may help to explain this paradox. Here, we test this conjecture by measuring the spontaneous mutation rate in a ubiquitous unicellular marine phytoplankton species Emiliania huxleyi (Haptophyta) that has modest genetic diversity despite an astronomically large population size. Genome sequencing of E. huxleyi mutation accumulation lines revealed 455 mutations, with an unusual GC-biased mutation spectrum. This yielded an estimate of the per site mutation rate µ = 5.55×10−10 (CI 95%: 5.05×10−10 – 6.09×10−10), which corresponds to an effective population size Ne ∼ 2.7×106. Such a modest Ne is surprising for a ubiquitous and abundant species that accounts for up to 10% of global primary productivity in the oceans. Our results indicate that even exceptionally large populations do not evolve mutation rates lower than ∼10−10 per nucleotide per cell division. Consequently, the extreme disparity between modest genetic diversity and astronomically large population size in the plankton species cannot be explained by an unusually low mutation rate.
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Edlund, Jeffrey A., et Christoph Adami. « Evolution of Robustness in Digital Organisms ». Artificial Life 10, no 2 (mars 2004) : 167–79. http://dx.doi.org/10.1162/106454604773563595.
Résumé :
We study the evolution of robustness in digital organisms adapting to a high mutation rate. As genomes adjust to the harsh mutational environment, the mean effect of single mutations decreases, up until the point where a sizable fraction (up to 30% in many cases) of the mutations are neutral. We correlate the changes in robustness along the line of descent to changes in directional epistasis, and find that increased robustness is achieved by moving from antagonistic epistasis between mutations towards codes where mutations are, on average, independent. We interpret this recoding as a breakup of linkage between vital sections of the genome, up to the point where instructions are maximally independent of each other. While such a recoding often requires sacrificing some replication speed, it is the best strategy for withstanding high rates of mutation.
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Komp Lindgren, Patricia, Åsa Karlsson et Diarmaid Hughes. « Mutation Rate and Evolution of Fluoroquinolone Resistance in Escherichia coli Isolates from Patients with Urinary Tract Infections ». Antimicrobial Agents and Chemotherapy 47, no 10 (octobre 2003) : 3222–32. http://dx.doi.org/10.1128/aac.47.10.3222-3232.2003.
Résumé :
ABSTRACT Escherichia coli strains from patients with uncomplicated urinary tract infections were examined by DNA sequencing for fluoroquinolone resistance-associated mutations in six genes: gyrA, gyrB, parC, parE, marOR, and acrR. The 54 strains analyzed had a susceptibility range distributed across 15 dilutions of the fluoroquinolone MICs. There was a correlation between the fluoroquinolone MIC and the number of resistance mutations that a strain carried, with resistant strains having mutations in two to five of these genes. Most resistant strains carried two mutations in gyrA and one mutation in parC. In addition, many resistant strains had mutations in parE, marOR, and/or acrR. No (resistance) mutation was found in gyrB. Thus, the evolution of fluoroquinolone resistance involves the accumulation of multiple mutations in several genes. The spontaneous mutation rate in these clinical strains varied by 2 orders of magnitude. A high mutation rate correlated strongly with a clinical resistance phenotype. This correlation suggests that an increased general mutation rate may play a significant role in the development of high-level resistance to fluoroquinolones by increasing the rate of accumulation of rare new mutations.
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Gerrish, Philip J., Alexandre Colato et Paul D. Sniegowski. « Genomic mutation rates that neutralize adaptive evolution and natural selection ». Journal of The Royal Society Interface 10, no 85 (6 août 2013) : 20130329. http://dx.doi.org/10.1098/rsif.2013.0329.
Résumé :
When mutation rates are low, natural selection remains effective, and increasing the mutation rate can give rise to an increase in adaptation rate. When mutation rates are high to begin with, however, increasing the mutation rate may have a detrimental effect because of the overwhelming presence of deleterious mutations. Indeed, if mutation rates are high enough: (i) adaptive evolution may be neutralized, resulting in a zero (or negative) adaptation rate despite the continued availability of adaptive and/or compensatory mutations, or (ii) natural selection may be neutralized, because the fitness of lineages bearing adaptive and/or compensatory mutations—whether established or newly arising—is eroded by excessive mutation, causing such lineages to decline in frequency. We apply these two criteria to a standard model of asexual adaptive evolution and derive mathematical expressions—some new, some old in new guise—delineating the mutation rates under which either adaptive evolution or natural selection is neutralized. The expressions are simple and require no a priori knowledge of organism- and/or environment-specific parameters. Our discussion connects these results to each other and to previous theory, showing convergence or equivalence of the different results in most cases.
Thèses sur le sujet "Mutation rate evolution":
1
Wilcox, A. « Evolution at a high imposed mutation rate ». Thesis, Nottingham Trent University, 2017. http://irep.ntu.ac.uk/id/eprint/32610/.
Résumé :
Mutation is an evolutionary process that provides much of the genetic variation required for natural selection and genetic drift. The mutation rate is a major driving force behind evolution, but is also an evolved characteristic itself. Although there is much theoretical research into why it evolved to the rate it did, there is little experimental work that investigates how its alteration affects evolution. I created a novel system in which bacteriophage ΦX174 could be evolved at a mutation rate two orders of magnitude higher than wild-type. This system used a defective proofreading gene in the host polymerase to cause mutagenesis, and did not require the use of external mutagens which often conferred a biased mutational spectrum and harmful non-mutagenic effects. Replicate populations of ΦX174 were evolved in both wild-type and mutagenic conditions for approximately 300 generations. One mutagenic population displayed a faster rate of adaptation than the wild-type lines, acquiring many of the same adaptive mutations in a shorter time frame, and rapidly increasing in fitness. While the wild-type lines were characterised by periodic selective sweeps of individual mutations, the mutagenic conditions allowed many of these mutations to rise in frequency due to a single selective sweep. The other mutagenic population, however, evolved very differently, with an early decrease in fitness that it did not recover from. This population acquired many mutations not seen in the other lines, and lacked many of the common adaptive mutations. The mutation rate increase was not high enough to cause extinction of the viral population. The vastly different outcomes for the two replicate populations show that while an elevated mutation rate can in turn increase the rate of adaptation, it can also prevent it altogether by altering the genetic background and "locking out" potential adaptive mutations through negative epistasis.
2
Krasovec, Marc. « Estimation des taux de mutation : implications pour la diversification et l'évolution du phytoplancton eucaryote ». Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066371/document.
Résumé :
Les mutations sont la principale source de diversité sur laquelle agit la sélection pour permettre aux espèces de s'adapter. Les études de l'effet des mutations sur la survie et du taux de mutation sont donc essentielles pour mieux comprendre l'évolution. Par une approche d'expérience d'accumulation de mutations, nous étudions ces deux questions chez cinq modèles d'algues vertes (Ostreococcus tauri, O. mediterraneus, Bathycoccus prasinos, Micromonas pusilla, et Picochlorum RCC4223). Il est mis en évidence une diminution de la fitness au cours du temps en raison des mutations délétères, et une importante interaction génotype-environnement sur l'effet des mutations. Le taux de mutation varie aux échelles intra-génomique et inter-spécifique, avec deux principaux résultats: une augmentation du taux de mutation dans les régions non codantes et une augmentation du taux de mutation avec la taille du génome chez les eucaryotes et en fonction de l'écart à l'équilibre en GC du génome. Aussi, l'assemblage et l'annotation d'une picoalgue du genre Picochlorum permettent d'étudier le rôle des transferts horizontaux de gènes chez les ChlorophytesMutations are the main source of diversity on which selection acts to allow species to adapt. Studies of the effect of mutations on survival and estimation of spontaneous mutation rates are essential to better understand evolution. Using mutation accumulation experimental approach, we investigated the issues of mutation effects and mutation rate in five models of green algae (Ostreococcus tauri, O. mediterraneus, Bathycoccus Prasinos, Micromonas pusilla, and Picochlorum RCC4223). It highlighted a decline in fitness over time because of deleterious mutations, and a significant genotype-environment interaction on the fitness effect of mutations. The mutation rate varies at inter-specific and intra-genomic scales, with two main results: a raise of the mutation rate in non-coding regions in accordance with trancriptional-coupled repair, and an increase of the mutation rate with an increase of the genome size in eukaryotes and the GC content deviation from the equilibrium. Also, a new Picochlorum genome is provided to investigate the role of horizontal gene transfer in the Chlorophyta group
3
Pietsch, Franziska. « Evolution of Antibiotic Resistance ». Doctoral thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-265018.
Résumé :
The emergence of antimicrobial resistance is a major global threat to modern medicine. The rapid dissemination of resistant pathogens and the associated loss of efficacy of many important drugs needs to be met with the development of new antibiotics and alternative treatment options. A better understanding of the evolution of resistance could help in developing strategies to slow down the spread of antimicrobial drug resistance. In this thesis we investigated the evolution of resistance to two important antibiotics, rifampicin and ciprofloxacin, paying special attention to the resistance patterns occurring with high frequency in clinical isolates. Rifampicin is a first-line drug in tuberculosis treatment and resistance to this valuable drug limits treatment options. Our work on rifampicin resistance helps to explain the extreme bias seen in the frequency of specific resistance mutations in resistant clinical isolates of M. tuberculosis. We identified an important interplay between the level of resistance, relative fitness and selection of fitness-compensatory mutations among the most common resistant isolates. Fluoroquinlones are widely used to treat infections with Gram-negatives and the frequency of resistance to these important drugs is increasing. Resistance to fluoroquinolones is the result of a multi-step evolutionary process. Our studies on the development of resistance to the fluoroquinolone drug ciprofloxacin provide insights into the evolutionary trajectories and reveal the order in which susceptible wild-type E. coli acquire multiple mutations leading to high level of resistance. We found that the evolution of ciprofloxacin resistance is strongly influenced by the mutation supply rate and by the relative fitness of competing strains at each successive step in the evolution. Our data show that different classes of resistance mutations arise in a particular, predictable order during drug selection. We also uncovered strong evidence for the existence of a novel class of mutations affecting transcription and translation, which contribute to the evolution of resistance to ciprofloxacin.
4
Krasovec, Marc. « Estimation des taux de mutation : implications pour la diversification et l'évolution du phytoplancton eucaryote ». Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066371.pdf.
Résumé :
Les mutations sont la principale source de diversité sur laquelle agit la sélection pour permettre aux espèces de s'adapter. Les études de l'effet des mutations sur la survie et du taux de mutation sont donc essentielles pour mieux comprendre l'évolution. Par une approche d'expérience d'accumulation de mutations, nous étudions ces deux questions chez cinq modèles d'algues vertes (Ostreococcus tauri, O. mediterraneus, Bathycoccus prasinos, Micromonas pusilla, et Picochlorum RCC4223). Il est mis en évidence une diminution de la fitness au cours du temps en raison des mutations délétères, et une importante interaction génotype-environnement sur l'effet des mutations. Le taux de mutation varie aux échelles intra-génomique et inter-spécifique, avec deux principaux résultats: une augmentation du taux de mutation dans les régions non codantes et une augmentation du taux de mutation avec la taille du génome chez les eucaryotes et en fonction de l'écart à l'équilibre en GC du génome. Aussi, l'assemblage et l'annotation d'une picoalgue du genre Picochlorum permettent d'étudier le rôle des transferts horizontaux de gènes chez les ChlorophytesMutations are the main source of diversity on which selection acts to allow species to adapt. Studies of the effect of mutations on survival and estimation of spontaneous mutation rates are essential to better understand evolution. Using mutation accumulation experimental approach, we investigated the issues of mutation effects and mutation rate in five models of green algae (Ostreococcus tauri, O. mediterraneus, Bathycoccus Prasinos, Micromonas pusilla, and Picochlorum RCC4223). It highlighted a decline in fitness over time because of deleterious mutations, and a significant genotype-environment interaction on the fitness effect of mutations. The mutation rate varies at inter-specific and intra-genomic scales, with two main results: a raise of the mutation rate in non-coding regions in accordance with trancriptional-coupled repair, and an increase of the mutation rate with an increase of the genome size in eukaryotes and the GC content deviation from the equilibrium. Also, a new Picochlorum genome is provided to investigate the role of horizontal gene transfer in the Chlorophyta group
5
Viraphong, Caudwell Larissa. « Dynamiques théorique et expérimentale des taux de mutations ». Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAV038/document.
Résumé :
Les mutations constituent une des principales sources de variation sur lesquelles agit la sélection naturelle, permettant ainsi l'évolution des organismes vivants. Comprendre la dynamique d'accumulation des mutations, ainsi que les biais pouvant influer leur apparition, est donc indispensable pour mieux appréhender les processus évolutifs. Dans cette thèse, j'ai exploré ces deux aspects dans un contexte évolutif.Dans une première partie, je me suis intéressée à la dynamique des taux de mutation au cours du temps évolutif. En effet, les mutations pouvant être bénéfiques, neutres ou délétères, la dynamique des taux de mutation est régie par deux forces opposées que sont l'adaptabilité (la capacité à évoluer) et la stabilité du génome. Cette dynamique a été très étudiée de façon théorique, mais les études expérimentales sont plus limitées, et surtout à des périodes de temps courtes.Dans une seconde partie, je me suis intéressée aux biais mutationnels. En effet, de précédentes études ont montré que les taux de mutation pouvaient varier au sein d'un même génome. Ainsi, certaines mutations peuvent se produire de façon plus fréquente que d'autres, le taux de mutation d'un nucléotide pouvant par exemple être influencé par les nucléotides avoisinants.Ces analyses ont été réalisées dans le contexte de l'expérience d'évolution à long terme initiée en 1988 par Richard Lenski (Michigan State University, USA). Douze populations ont été initiées à partir d'un ancêtre commun Escherichia coli et sont propagées depuis plus de 25 ans par repiquages quotidiens dans un milieu frais. Des échantillons ont été prélevés et le génome de clones évolués séquencé à différents temps, permettant une étude phénotypique et génomique des taux de mutations sur plus de 50 000 générations.J'ai ainsi pu mettre en évidence une dynamique importante des taux de mutation, avec l'émergence de génotypes hypermutateurs suivie de phénomènes de compensation multiples. D'autre part, j'ai pu observer des biais mutationnels importants dont l'impact des nucléotides avoisinant les mutations silencieuses dans les populationsMutations are the ultimate source of variation that allow living organisms to adapt through natural selection. Understanding the dynamics of mutation accumulation and how they are biased stands as a keystone to understand evolutionary processes. In this work, I explored these two aspects of mutation accumulation in an evolutionary framework.First, I studied the dynamics of mutation rates over evolutionary time. As mutations may be beneficial, neutral or deleterious, the dynamics of mutation rates will be a function of two opposite driving forces: evolvability or the ability to evolve and genome stability. The resulting dynamics has been widely studied theoretically but experimental studies are scarce and mostly limited to short periods of time.Second, I focused on mutational biases. Previous studies showed that mutation rates might vary within given genomes, as a function for example of both their localization and neighboring nucleotides.All studies from this Ph.D thesis were performed in the context of the long-term evolution experiment which has been started in 1988 by Richard Lenski (Michigan State University, USA). Twelve populations were initiated from a common ancestor strain of Escherichia coli and have been propagated ever since for more than 25 years by daily transfers in fresh medium. Samples were collected and genomes of evolved clones were sequenced at regular time point intervals, allowing both the phenotypic and genomic studies of the mutation rate for more than 50,000 generations.In this study, I showed that mutation rates are highly dynamic: the emergence of hypermutator genotypes is followed by multiple compensation events. I also observed large mutational biases, including the impact of the neighboring nucleotides on resulting aminoacid changes
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Berlin, Sofia. « The Effects of Mutation and Selection on the Rate and Pattern of Molecular Evolution in Birds ». Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4516.
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Ally, Dilara. « The cost of longevity : loss of sexual function in natural clones of Populus tremuloides ». Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/282.
Résumé :
Most clonal plants exhibit a modular structure at multiple levels. At the level of the organs, they are characterized by functional modules, such as, internodes, leaves, branches. At the level of the genetic individual (clone or genet), they possess independent evolutionary and physiological units (ramets). These evolutionary units arise through the widespread phenomenon of clonal reproduction, achieved in a variety of ways including rhizomes, stolons, bulbils, or lateral roots. The focus of this study was Populus tremuloides, trembling aspen, a dioecious tree that reproduces sexually by seed and asexually through lateral roots. Local forest patches in western populations of Populus tremuloides consisted largely of multiple genotypes. Multi-clonal patches were dominated by a single genotype, and in one population (Riske Creek) we found several patches (five out of 17) consisting of a single genotype. A second consequence of modularity is that during the repeated cycle of ramet birth, development and death, somatic mutations have the opportunity to occur. Eventually, the clone becomes a mosaic of mutant and non-mutant cell lineages. We found that neutral somatic mutations accumulated across 14 microsatellite loci at a rate of between 10^-6 and 10^-5 per locus per year. We suggest that neutral genetic divergence, under a star phylogeny model of clonal growth, is an alternative way to estimate clone age. Previous estimates of clone age couple the mean growth rate per year of shoots with the area covered by the clone. This assumes a positive linear relationship between clone age and clone size. We found, however, no repeatable pattern across our populations in terms of the relationship of either shape or size to the number of somatic changes. A final consequence of modularity is that during clonal growth, natural selection is relaxed for traits involving sexual function. This means that mutations deleterious to sexual function can accumulate, reducing the overall sexual fitness of a clone. We coupled neutral genetic divergence within clones with pollen fitness data to infer the rate and effect of mildly deleterious mutations. Mutations reduced relative sexual fitness in clonal aspen populations by about 0.12x10^-3 to 1.01x10^-3 per year. Furthermore, the decline in sexual function with clone age is evidence that clonal organisms are vulnerable to the effects of senescence.
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Mugal, Carina Farah. « Nucleotide Substitution Patterns in Vertebrate Genomes ». Doctoral thesis, Uppsala universitet, Evolutionsbiologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-198787.
Résumé :
The rates and patterns at which nucleotide substitutions occur vary significantly across the genome sequence of vertebrates. A prominent example is the difference in the rate of evolution of functional sequences versus nonfunctional (neutrally evolving) sequences, which is explained by the influence of natural selection on functional sequences. However, even within neutrally evolving sequences there is striking variation in the rates and patterns of nucleotide substitutions. Unraveling the underlying processes that induce this variation is necessary to understand the basic principles of variation in neutral substitution profiles, which in turn is crucial for the identification of regions in the genome where natural selection acts. This research question builds the main focus of the present thesis. I have studied the causes and consequences of variation in different patterns of nucleotide substitutions. In particular, I have investigated substitutional strand asymmetries in mammalian genes and could show that they result from the asymmetric nature of DNA replication and transcription. Comparative analysis of substitutional asymmetries then suggested that the organization of DNA replication and the level of transcription are conserved among mammals. Further, I have examined the variation in CpG mutation rate among human genes and could show that beside DNA methylation also GC content plays a decisive role in CpG mutability. In addition, I have studied the signatures of GC-biased gene conversion and its impact on the evolution of the GC isochore structure in chicken. By comparison of the results in chicken to previous results in human I found evidence that karyotype stability is critical for the evolution of GC isochores. Finally, beside the empirical studies, I have performed theoretical investigations of substitution rates in functional sequences. More precisely, I have explored the temporal dynamics of estimates of the ratio of non-synonymous to synonymous substitution rates dN/dS in a phylogentic-population genetic framework.
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Axelsson, Erik. « Comparative Genomics in Birds ». Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7432.
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Saclier, Nathanaëlle. « Origine des variations de taux d’évolution moléculaire inter-spécifiques : apport d’un modèle génomique en milieu souterrain ». Thesis, Lyon, 2019. https://n2t.net/ark:/47881/m69p310z.
Résumé :
La vitesse à laquelle les séquences d’ADN évoluent varie selon les espèces. Ces différences peuvent venir de caractéristiques intrinsèques de l’espèce (taux métabolique, traits d’histoire de vie) ou de son environnement (rayonnements ionisants). L’objectif de cette thèse est de tester les principales hypothèses expliquant les variations de taux d’évolution moléculaire entre les espèces. Pour cela, les particularités des Asellidae souterrains ont été couplées avec des données de séquençage nouvelle génération dans le génome nucléaire et le génome mitochondrial. L’utilisation des Asellidae comme modèle biologique nous permet d’avoir, au sein du même groupe, des espèces ayant indépendamment effectuées une transition vers le milieu souterrain. Cette transition étant accompagnée de nombreux changements, tant biologiques (longévité, taux métabolique, temps de génération) qu’environnementaux, elle nous permet, au sein du même groupe, de pouvoir comparer des espèces contrastées en termes de longévité, de taille de populations, de rayonnements ionisants ou encore de productivité et de température. De plus, parce que ces organismes dispersent peu, ils persistent dans le même environnement durant de nombreuses générations, permettant de préciser et de quantifier les facteurs responsables de variations du taux d’évolution moléculaire entre les espèces.Cette approche nous a permis de mettre en évidence un effet du temps de génération sur le taux d’évolution du génome nucléaire mais pas sur le génome mitochondrial. Un effet de la radioactivité naturelle, d’une ampleur analogue à celle du temps de génération a également été mis en évidence. Enfin, l’étude des variations des taux d’évolution moléculaire à une échelle globale a révélée des biais dans les calculs des taux de substitutions qui devront être pris en compte dans les études cherchant a établir le lien entre le taux de mutations et la diversificationThe rate at which DNA accumulates substitutions varies widely among species. Rate variations have been imputed to species intrinsic features (metabolic rate, life history traits) or to the environment characteristics (ionizing radiations, selection pressure). The aim of this PhD project was to investigate the main hypotheses explaining variations in the rate of molecular evolution between species. To achieve that, we combined the unique properties of subterranean isopods from the Asellidae family and high-throughput sequencing data from the nuclear and mitochondrial genome. Asellidae species have made multiple independent transitions to subterranean environments where subterranean species have repeatedly evolved a lower metabolic rate, a longer lifespan and a longer generation time. Moreover, because they are poor dispersers, they are exposed to the same environment across many generations, allowing us to compare species with long-term contrasted features in term of life history traits and environmental characteristics. We found that generation time negatively impact the rate of molecular evolution in the nuclear genome whereas the mitochondrial rate remained unchanged. We also found an increase of the mutation rate for species living in naturally highly radioactive environments. Finally, the study of the rate of molecular evolution variation at a global scale brought forward a systematic bias which needs to be taken into account in studying the link between the mutation rate and diversification
Livres sur le sujet "Mutation rate evolution":
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Walsh, Bruce, et Michael Lynch. The Nonadaptive Forces of Evolution. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198830870.003.0004.
Résumé :
This chapter examines the relative strengths of the nonadaptive evolutionary forces (drift, mutation, recombination) acting on genomes. It reviews estimators for effective population size, mutation rate, and recombination rate, and summarizes the known genomic results over a wide range of taxa. The mutation rate tends to be lower in organisms with larger effective population sizes, consistent with the drift-barrier hypothesis wherein selection is ineffective when it is less than the reciprocal of the effective population size.
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Frankham, Richard, Jonathan D. Ballou, Katherine Ralls, Mark D. B. Eldridge, Michele R. Dudash, Charles B. Fenster, Robert C. Lacy et Paul Sunnucks. Loss of genetic diversity reduces ability to adapt. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198783398.003.0004.
Résumé :
Environmental change is a ubiquitous feature of the conditions faced by species, so they must either evolve, move to avoid threats, or perish. Species require genetic diversity to evolve to cope with environmental change through natural selection (adaptive evolution). The ability of populations to undergo adaptive evolution depends upon the strength of selection, genetic diversity, effective population size, mutation rates and number of generations. Loss of genetic diversity in small populations reduces their ability to evolve to cope with environmental change, thus increasing their extinction risk. Adaptive evolution in the short to medium term predominantly utilizes pre-existing genetic diversity, but new mutations make increasing contributions in later generations. Evolutionary potential can be estimated from the heritability of fitness in the environment of interest, or by extrapolation from genomic diversity.
Chapitres de livres sur le sujet "Mutation rate evolution":
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Zeng, Ling-Wen, Josep M. Comeron, Bin Chen et Martin Kreitman. « The molecular clock revisited : the rate of synonymous vs. replacement change in Drosophila ». Dans Mutation and Evolution, 369–82. Dordrecht : Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5210-5_30.
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García-Dorado, Aurora, Juan L. Monedero et Carlos López-Fanjul. « The mutation rate and the distribution of mutational effects of viability and fitness in Drosophila melanogaster ». Dans Mutation and Evolution, 255–65. Dordrecht : Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5210-5_21.
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Ewald, Paul W. « Evolution of mutation rate and virulence among human retroviruses ». Dans Infection, Polymorphism and Evolution, 63–73. Dordrecht : Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-009-0077-6_7.
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Omeradzic, Amir, et Hans-Georg Beyer. « Progress Rate Analysis of Evolution Strategies on the Rastrigin Function : First Results ». Dans Lecture Notes in Computer Science, 499–511. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-14721-0_35.
Résumé :
AbstractA first order progress rate is derived for the intermediate multi-recombinative Evolution Strategy $$(\mu /\mu _I, \lambda )$$ ( μ / μ I , λ ) -ES on the highly multimodal Rastrigin test function. The progress is derived within a linearized model applying the method of so-called noisy order statistics. To this end, the mutation-induced variance of the Rastrigin function is determined. The obtained progress approximation is compared to simulations and yields strengths and limitations depending on mutation strength and distance to the optimizer. Furthermore, the progress is iterated using the dynamical systems approach and compared to averaged optimization runs. The property of global convergence within given approximation is discussed. As an outlook, the need of an improved first order progress rate as well as the extension to higher order progress including positional fluctuations is explained.
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Nov, Yuval. « Probabilistic Methods in Directed Evolution : Library Size, Mutation Rate, and Diversity ». Dans Methods in Molecular Biology, 261–78. New York, NY : Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-1053-3_18.
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Klekowski, Edward J. « Mutation rates in mangroves and other plants ». Dans Mutation and Evolution, 325–31. Dordrecht : Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5210-5_26.
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Johnston, Mark O. « Evolution of intermediate selfing rates in plants : pollination ecology versus deleterious mutations ». Dans Mutation and Evolution, 267–78. Dordrecht : Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5210-5_22.
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Caballero, Armando, et Peter D. Keightley. « Inferences on genome-wide deleterious mutation rates in inbred populations of Drosophila and mice ». Dans Mutation and Evolution, 229–39. Dordrecht : Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5210-5_19.
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Pita, Justin S., et Marilyn J. Roossinck. « Virus Populations, Mutation Rates and Frequencies ». Dans Plant Virus Evolution, 109–21. Berlin, Heidelberg : Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-75763-4_6.
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Drake, John W. « Rates of Spontaneous Mutation : Insights Gained Over the Last Half Century ». Dans Genetics, Evolution and Radiation, 77–84. Cham : Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-48838-7_7.
Actes de conférences sur le sujet "Mutation rate evolution":
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Soon, Gan Kim, Patricia Anthony, Jason Teo et Chin Kim On. « The effect of mutation rate in the evolution of bidding strategies ». Dans 2008 International Symposium on Information Technology. IEEE, 2008. http://dx.doi.org/10.1109/itsim.2008.4631588.
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Benslimane, Fatiha M., Hebah Al Khatib, Dana Albatesh, Ola Al-Jamal, Sonia Boughattas, Asmaa A. Althani et Hadi M. Yassine. « Nanopore Sequencing SARS-CoV-2 Genome in Qatar ». Dans Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2020. http://dx.doi.org/10.29117/quarfe.2020.0289.
Résumé :
Background: The current pandemic, COVID-19, is cause by an RNA Coronavirus that was recently identified as SARS-CoV-2. RNA viruses tend to have a high mutation rate; the rate is around a million times greater than that of their hosts. The mutagenic potential of the virus depends on many factors, including the fidelity of nucleic acid-replicating viral enzymes, such as SARSCoV-2 RNA dependent RNA polymerase (RdRp). The rate of mutation drives viral evolution and genome variability, consequently allowing viruses to escape the immunity of the host and develop resistance to drugs. Therefore, the characterization of SARS-CoV-2 variants might lead to implement better therapeutics treatments, vaccines design and identify new diagnostics approaches. Aim: The aim of this study was to establish a fast sequencing method to identify SARS-CoV-2 mutations in Qatar. This will help to assess if there are new viral variants that are spreading in country. Methods: RNA was isolated from samples collected from Qatar COVID-19 positive patients. The Artic Network V3 primer scheme and Oxford Nanopore ligation sequencing kit were used to prepare the sequencing libraries. Libraries were loaded on to R9.4.1 flow cells and ran on a GridION. Bioinformatics analysis was done following the Artic Network SARA-CoV-2 bioinformatics tools. Results: Genome coverage of sequenced samples was >80% and the depth was average at 200x. The coverage was highly dependable on sample viral load; samples of CT value lower than 30 resulted in better sequence coverage. The sequenced genomes were deposited in GISAID and were mainly clustering with genomes deposited from the UK. Sequences were compared to Illumina and sanger sequences and they showed compatible results. Conclusion: The use of ONT to sequence SARA-CoV-2 is a quick, affordable, and reliable technique to determine viral mutation. Using this technique, the first sequences from Qatar were deposited in to GISAID. Up to date, 700 genomes have been sequenced from Qatari samples.
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Pranav, P., et G. Jeyakumar. « Control parameter adaptation strategies for mutation and crossover rates of differential evolution algorithm - An insight ». Dans 2015 IEEE International Conference on Computational Intelligence and Computing Research (ICCIC). IEEE, 2015. http://dx.doi.org/10.1109/iccic.2015.7435788.
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Perini, Laís Bissoli, Fernando Zanette, Katia Lin, Pricila Bernardi, Gisele Espíndola et André Dias de Oliveira. « Mutation in the REEP1 gene related to SPG31 (Autosomal Dominant Hereditary Spastic Paraplegia type 31) ». Dans XIV Congresso Paulista de Neurologia. Zeppelini Editorial e Comunicação, 2023. http://dx.doi.org/10.5327/1516-3180.141s1.760.
Résumé :
Introduction: The REEP1 gene is associated with a spectrum of overlapping autosomal dominant conditions including hereditary spastic paraplegia 31 (SPG31), distal hereditary motor neuropathy 5B. It’s a neurologic condition limited to progressive lower extremity spastic weakness and associated atrophy, distally predominant, hypertonic urinary bladder, and mild lower extremit vibratory sensation loss. SPG31 has an estimated prevalence of one to 12 per 100.000 individuals. Objectives: To report a rare case of mutation in the REEP1 gene related to SPG31. Case presentation: A 38-year-old woman, born to non-consanguineous parents, presented with difficulty walking and frequent falls since the age of 11, with slow progressive evolution, accompanied by cramps in the lower limbs. The patient hasd an extensive family history (father, dizygotic twin sister, paternal grandmother, and three paternal uncles). Physical examination of the lower limbs revealed spasticity, proximal muscle strength grade 4+ and distal muscle strength grade 4-, grade 4 hyperreflexia in the patellar and Achilles tendons, with an inextinguishable plantar clonus and bilateral Babinski sign, and slight hypotrophy of the gastrocnemius muscles were observed, as well as spastic gait. The patient hasd urge urinary incontinence with partial remission using Oxibutynin. Baclofen 20 mg/day is being used to control spasticity. Genetic testing was performed and revealed the c.128_138dup mutation (p.Phe48Tyrfs*25) in heterozygous in the REEP1 gene related to SPG31 (Autosomal Dominant Hereditary Spastic Paraplegia type 31). Conclusion: As the diagnosis of hereditary spastic paraplegia 31 associated to a REEP1 gene mutation is rare, neurologists may have limited knowledge of this condition, precluding its adequate diagnosis. The urge urinary incontinence is a distinctive feature, and should raise awareness for this condition.
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Iegoroff, Renan, Rafael Herlan Terceros Vaca, Gustavo Araújo Pinheiro, Alvaro Marcelo Huchani Huanca, Matheus Henrique de Souza Coradini et Leonardo Mariano Inácio Medeiros. « Cadasil, atypical and familial presentation – family case report ». Dans XIV Congresso Paulista de Neurologia. Zeppelini Editorial e Comunicação, 2023. http://dx.doi.org/10.5327/1516-3180.141s1.318.
Résumé :
Introduction: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), is a non-atherosclerotic, nonamyloid, hereditary cerebral disease of small vessels and capillaries caused by mutations in the NOTCH-3 gene located on chromosome 19. The presence of granular osmophilic material (GOM) deposition in the smooth muscle cells of vessel walls is the pathological hallmark of arteriopathy in CADASIL. GOM deposits in the basal lamina of smooth muscle of small vessels are pathognomonic for CADASIL. The presence of GOM in capillary blood vessels of the skin and muscle in biopsy and genetic studies (NOTCH-3 analysis) plays a key diagnostic role. Biopsy tests have high specificity (up to 100%) and low sensitivity (less than 50%). The NOTCH-3 test has been proposed as the primary diagnostic approach, allowing detection of 90% of affected individuals. CADASIL has an estimated prevalence between 2 and 5 in 100,000, and the phenotypic study demonstrates different clinical symptoms in the course of the disease within the same family. The average age of onset of clinical symptoms varies between 48.3 years in men and 52.2 years in women. Characteristic symptoms of migraine, stroke or TIA (transient ischemic attack), behavioral changes, early and progressive cognitive changes associated with leukoencephalopathy on imaging studies. The large association of symptoms often causes the diagnosis of CADASIL to be delayed. In this case, we had an association of gait ataxia within the framework of motor alterations, demonstrating the wide range of symptomatology of the pathology. This case report presents a familial course that started outside the most prevalent age group in the studies described and with an atypical presentation in an affected generation. Case reports: Case 01: woman, 68 years old, started progressively forgetting to perform household activities after the age of fifty, associated with primarily generalized myoclonic epileptic seizures, evolving rapidly within five years to walking apraxia with the use of a wheelchair and tonic-tonic epileptic seizures. bilateral clonic disorders, comprehension aphasia and bradypsychism. Relatives report previous migraine without chronic aura and REM (rapid eye movement sleep) sleep behavior disorder (RMSD). On neurological examination, severe ataxia with bilateral dysdiadochokinesia associated with bilateral hypometric index-index. Bilateral ROT 4+/4+ with bilateral Hoffman and Babinski signs. MMSS and MMII with FGM 4/5 proximal and distal. Case 02: woman, 36 years old, pastry chef, had episodes of forgetting about everyday activities of her work, progressive in the last three years (cake recipes, budget accounts, orders placed) associated with confusion for spatial location on the way home/ work, evolving to apraxia in writing letters and words and difficulty with calculations associated with monoparesis of the right lower limb for twelve months with progression to paresis of the lower limbs after six months and evolution to paresthesia of the upper limbs for three months. Associated with the condition, he has migraine without chronic aura and RMSD. The neurological examination showed Mini-Mental State Examination 22/30 (expected score of 29), list of animals in one minute: 09 animals; list of words starting with “F”: 03 words; clock test: 2/4; difficulty with calculations and digital agnosia with right/left apraxia; Upper limbs: eutrophic, FMG 4/5, bilateral distal; FMG 5/5 bilateral proximal; Lower limbs: eutrophic, bilateral FMG 4/5 distal and proximal with positive Mingazini; atypical gait with evidenced weakness in heel, toe and tandem gait; Bilateral dysdiadochokinesia with eumetric, slowed indexindex; ROT 4+/4+ in the right side with positive Hoffman and Babinski signs. MRI Brain (17/09/2020): extensive area of hypersignal on T2 and FLAIR (T2- weighted-Fluid-Attenuated Inversion Recovery) involving the periventricular white matter in all lobes without atrophic or expansive effect; Case 03: woman, 45 years old, started behavioral arrest epileptic seizures at the age of thirty-two, progressing to focal dysperceptive seizures with progression to bilateral tonic clonic seizures after eight months and multiple episodes of anterograde amnesia, presenting forgetfulness related to everyday work activities (exchanged worksheets , payments, calculation errors and budgets); associated with the condition presented migraine without chronic aura and RMSD. Genetic Test (04/06/2017): Heterozygous alteration in exon 8 of the NOTHC – 3 gene. Discussion: CADASIL presents a rare cause of cognitive decline and is often overlooked in diagnosis, except in cases of high clinical suspicion in a familial course. Access to imaging tests becomes fundamental for the diagnostic segment and the primordial genetic test for etiological elucidation and family planning, in the report described the family presentation with the same course of satellite symptoms (migraine without aura, and RMSD) associated with cognitive alteration with anticipation of age of onset are hallmarks of clinical thinking. Cases described in the literature show that the clinical symptomatology is not necessarily related to the level of brain injury observed in the imaging exam, which could be explained by personal factors and which exon is affected. The NOTCH-3 gene has 24 exons, in which the literature reports exon 4 as the most common mutation, followed by 3, 5 and 6, mainly in the Caucasian population. In an Asian population, the most affected exon is 4 and 11, which is also found in Italian descendants. The mutation in exon 8, described in the clinical case, is found in a population of Portuguese origin, being the second most common mutation in this nationality, behind the mutation in exon 4. Brain MRI studies have tried to elucidate the most affected brain regions, aiming to trace a line of evolution. Involvement of the temporal lobe, external capsule and corpus callosum are described as probable markers of CADASIL, and can be used as an aid in the diagnosis due to its specificity of 86% and sensitivity of 89%. Studies also show that the frontoparietal area has frequent findings of hyperintensity (100%), followed by the temporal lobe (83%), less frequently affecting the brainstem, occipital lobe and cerebellum. Despite the great advances in the specialized literature, the causes of the important cognitive dysfunction presented in the course of the evolution of CADASIL remain unclear. However, studies have suggested that the process of cognitive decline is more related to the loss of cortico-subcortical connections than to brain atrophy itself, with these disconnections resulting from repeated transient ischemic accidents. Science has been looking for ways to change the prognosis of CADASIL, recent studies in gene therapy and neurogenetics show the importance of thinking about this pathology as a genetic disease of great importance to change the prognosis of this pathology.
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Leonor, Ana, et Madeira Rodrigues. « Drawing as a Periphery in Architectural Learning ». Dans 1995 ACSA International Conference. ACSA Press, 1995. http://dx.doi.org/10.35483/acsa.intl.1995.35.
Résumé :
The conquest of a dominant place over the members of the same race, with the result of using the power such a place allows and having the acceptance of the other members for being the leaders is a characteristic of the adult relationship between almost all animal species. The former time of childhood was dedicated to the imitation of the adults and to the experimenting of behaviors, or, in other words, learning and playing. Humberto Maturama believes that humans are, in behavioral tenns, an exception, as the time of childhood is extended throughout most adult life, which defines us humans as a neotenic race, and with the use of other behaviors, we have transformed what is the usual master/slave relation of adult members from other races. Like this, the family in the way we live it, becomes a human-invented structure that implies relationships between its members which are bounded by mutual trust and love. Mutatis mutandis we spend our life repeating relationships that use the same pattern. In this way, love would be the main engine of evolution and also our greatest invention.
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Barbosa, Alana Strucker, Camila Alves Pereira, Vanessa de Freitas Moreira, Igor Braga Farias, Paulo de Lima Serrano, Bruno de Mattos Lombardi Badia, Hélvia Bertoldo de Oliveira, Wladimir Bocca Vieira de Rezende Pinto, Paulo Victor Sgobbi de Souza et Acary Souza Bulle Oliveira. « Case report : myofasciitis associated with the NFkB gene ». Dans XIV Congresso Paulista de Neurologia. Zeppelini Editorial e Comunicação, 2023. http://dx.doi.org/10.5327/1516-3180.141s1.771.
Résumé :
A male patient, 44-year-old, presents with severe abrupt myalgia in the upper and lower limbs, with evolution to muscle weakness after two weeks. After 40 days, he developed intermittent fever and night sweats. Personal history of anorectal abscess drainage. The neurological exam evidenced discreet muscular hypotrophy of the lateral and medial portion of the thighs, global hyperreflexia, proximal muscle weakness, and bilateral antalgic gait. A right vastus lateralis muscle biopsy showed muscle atrophy and congested vessels. Magnetic resonance imaging of the thighs visualizes diffuse inflammation of the fascia and muscles of the thigh. After beginning the use of corticosteroids, there was a significant improvement. A genetic test showing the c.1129G>A variant (p.Gly377Ser) in the NFKB1 gene was also requested, followed by corticoid weaning and human immunoglobulin initiation.Myofasciitis is a painful inflammatory condition affecting the muscles and the tissues around them. One of them is the fascia, a fibrous connective tissue that surrounds and connects the body’s muscles, tendons, and bones. The pathogenesis may be founded on the mutation of the NFkB gene, which regulates our body’s inflammatory and immune processes, which may result in autoinflammatory diseases, immunodeficiencies, and, consequently, tissue damage. Symptoms are varied and can include muscle weakness, arthralgia, and skin rashes. Diagnosis is based on blood tests, imaging, muscle biopsy, and genetic testing. Treatment involves rehabilitation and immunosuppressive medications to control the immune system’s response. Although NFkB-associated myofasciitis is rare, awareness and understanding of its symptoms are essential to ensure early diagnosis and appropriate treatment.
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Reis, Gabriel Baêta Branquinho, Hugo Francisco da Fonseca Neto, Alice Jardim Zaccariotti, Daniel Bispo de Sousa, Silvaleide Ataides Assunção, Thiago Martins de Abreu, Fernando Santos de Azevedo et Lanúscia Morais de Santana. « INVASIVE DUCTAL CARCINOMA IN A PATIENT WITH LI-FRAUMENI SYNDROME : A CASE REPORT ». Dans Abstracts from the Brazilian Breast Cancer Symposium - BBCS 2021. Mastology, 2021. http://dx.doi.org/10.29289/259453942021v31s2105.
Résumé :
Introduction/Objectives: Breast cancer is one of the most common malignancies among women, with 10% resulting from genetic predisposition. Li-Fraumeni syndrome is an autosomal dominant disease that predisposes to multiple primary tumors and is responsible for less than 0.1% of breast cancers, being considered in early-onset tumors. The aim of this report was to describe a fast evolution of three primary tumors in a young patient with Li-Fraumeni syndrome, including ductal breast carcinoma. Case Report: In 2017, a 27-year-old female patient was diagnosed with malignant cancer of the right breast, Luminal HER KI67 70%, clinical stage IV (liver and lung), underwent first-line cancer treatment, maintaining endocrinotherapy and Double Block, with a positive genetic panel test for TP53 mutation, inferring SLF. In 2018, screening colonoscopy showed colon adenocarcinoma, pT53pN1, treated with total colectomy with ileal pouch, followed by suspension of endocrinotherapy and maintenance of Double Block and adjuvant FOLFOX. At the end of chemotherapy, endocrinotherapy was adopted again. Reassessment tests showed partial response in the liver, but the primary nodules were unchanged. Biopsy after thoracoscopy described lung adenocarcinoma, pT3pN2, submitted to adjuvant with Gemzar and Navelbine, followed by Double Block and interruption of endocrinotherapy. It evolved with the appearance of nodules in the right breast, suggestive of progression of breast disease, under treatment with Xeloda, Herceptin, and Perjeta, showing good clinical response. Discussion: Breast cancer in young people increases the possibility of heredity, thus raising the need for investigations of genetic syndromes. Although rare, the identification of FHL brings an important implication for the genetic counseling. Early diagnosis is the best form of management, enabling the preventive screening and intervention of multiple malignancies. Conclusion: Cases of breast cancer in young women should raise a suspected diagnosis of Li-Fraumeni syndrome, which can change the therapeutic and investigation of other cancers at an early stage.
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Maia, Fernanda Pimentel Arraes, Maria Clara Tomaz Feijão, Emanuel Cintra Austregésilo Bezerra, Ana Carolina Filgueiras Teles et Luiz Gonzaga Porto Pinheiro. « MALE BREAST CANCER AFTER LIVER TRANSPLANTATION : A CASE REPORT ». Dans XXIV Congresso Brasileiro de Mastologia. Mastology, 2022. http://dx.doi.org/10.29289/259453942022v32s1053.
Résumé :
Male breast cancer (MBC) is an uncommon disease representing only 1% of the total cases. This low incident rate could be due to the low amount of breast tissue and the hormonal differences between men and women. The Surveillance, Epidemiology and End Result (SEER) program reported that the incidence rate of breast cancer was 1.1 per 100,000 men in the mid-1970s and raised to 1.44 per 100,000 men by 2010. There are a lot of characteristics that are common to male and female breast carcinomas, especially given the fact that a lot of the factors that influence malignant changes are similar, but there are also some singularities. In this matter, it is important to understand the existence of risk factors for MBC, particularly the genetic abnormalities, such as BRCA-1 and BRCA-2 mutations. Therefore, a man with this type of predisposition is more likely to develop breast cancer, especially if submitted to an immunosuppressive therapy, normally used to prevent the rejection of transplanted organs. This study aimed to report a case of a patient with chronic alcoholism history, who later developed a liver tumor and breast cancer. This patient reported gynecomastia, which could be related to his health condition, given the fact that liver failure and cirrhosis probably started preventing the inactivation of the estrogens by the liver, causing and stimulating proliferation of the mammary tissue, and increasing the chance of gene mutations. We report a 56-year-old man with a history of smoking, chronic alcoholism, and gynecomastia with 10 years of evolution who was diagnosed with cirrhosis and liver tumor in 2014. He underwent two sessions of a chemoradiotherapy treatment, resulting in reduction of the tumor size as a result. In 2015, the patient had a liver transplant. To prevent organ rejection, it was established an immunosuppressive therapy with tacrolimus 10 mg/day and myfortic 720 mg/day. In 2016, the patient noticed a breast lump and searched for medical assistance. At the appointment, after physical examination, the presence of a 2-×2-cm lump in the right breast was confirmed. A few examinations were requested, such as ultrasonography, which showed a BIRADS4 as a result, chest tomography, and abdominal tomography. The examinations concluded that the lump had a high probability of malignancy. Then, to confirm the suspicion, it was proposed the performance of a fine-needle aspiration of the lump was followed by a core biopsy. The results showed an invasive breast carcinoma positive for estrogen receptors, negative for progesterone receptors, negative for HER-2 oncoprotein, and KI67 5%. Therefore, the molecular classification by immunohistochemistry is a LUMINAL A, which indicates the possibility of a better prognosis. A few days later, the patient was submitted for a radical mastectomy on the right breast. During the surgery, it was also performed a sentinel lymph nodes (SLN) scintigraphy and analysis of the material collected from the right breast. The conclusion expressed positive screening for malignant cells, two lymph nodes compromised by macrometastasis (large focus measuring 1.2 cm with capsular transposition associated) and positive screening for malignant cells suggestive of carcinoma. The tumor, according to a grading system, presented a Scarff-Bloom Richardson modified by Elston and Ellis grade III, with tubular grade 3, nuclear grade 3, and mitotic index 2. It was also identified as focal tumor necrosis, vascular invasion, and perineural invasion. The pathological staging of the tumor was pT2 pN1a (SN+) pMx.
Rapports d'organisations sur le sujet "Mutation rate evolution":
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Schuster, Gadi, et David Stern. Integration of phosphorus and chloroplast mRNA metabolism through regulated ribonucleases. United States Department of Agriculture, août 2008. http://dx.doi.org/10.32747/2008.7695859.bard.
Résumé :
New potential for engineering chloroplasts to express novel traits has stimulated research into relevant techniques and genetic processes, including plastid transformation and gene regulation. This proposal continued our long time BARD-funded collaboration research into mechanisms that influence chloroplast RNA accumulation, and thus gene expression. Previous work on cpRNA catabolism has elucidated a pathway initiated by endonucleolytic cleavage, followed by polyadenylation and exonucleolytic degradation. A major player in this process is the nucleus-encoded exoribonuclease/polymerasepolynucleotidephoshorylase (PNPase). Biochemical characterization of PNPase has revealed a modular structure that controls its RNA synthesis and degradation activities, which in turn are responsive to the phosphate (P) concentration. However, the in vivo roles and regulation of these opposing activities are poorly understood. The objectives of this project were to define how PNPase is controlled by P and nucleotides, using in vitro assays; To make use of both null and site-directed mutations in the PNPgene to study why PNPase appears to be required for photosynthesis; and to analyze plants defective in P sensing for effects on chloroplast gene expression, to address one aspect of how adaptation is integrated throughout the organism. Our new data show that P deprivation reduces cpRNA decay rates in vivo in a PNPasedependent manner, suggesting that PNPase is part of an organismal P limitation response chain that includes the chloroplast. As an essential component of macromolecules, P availability often limits plant growth, and particularly impacts photosynthesis. Although plants have evolved sophisticated scavenging mechanisms these have yet to be exploited, hence P is the most important fertilizer input for crop plants. cpRNA metabolism was found to be regulated by P concentrations through a global sensing pathway in which PNPase is a central player. In addition several additional discoveries were revealed during the course of this research program. The human mitochondria PNPase was explored and a possible role in maintaining mitochondria homeostasis was outlined. As polyadenylation was found to be a common mechanism that is present in almost all organisms, the few examples of organisms that metabolize RNA with no polyadenylation were analyzed and described. Our experiment shaded new insights into how nutrient stress signals affect yield by influencing photosynthesis and other chloroplast processes, suggesting strategies for improving agriculturally-important plants or plants with novel introduced traits. Our studies illuminated the poorly understood linkage of chloroplast gene expression to environmental influences other than light quality and quantity. Finely, our finding significantly advanced the knowledge about polyadenylation of RNA, the evolution of this process and its function in different organisms including bacteria, archaea, chloroplasts, mitochondria and the eukaryotic cell. These new insights into chloroplast gene regulation will ultimately support plant improvement for agriculture