Muller Ratchet
Mostrando 1-12 de 26 artigos, teses e dissertações.
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1. Uma abordagem estocástica da evolução do sexo e recombinação / Uma abordagem estocástica da evolução do sexo e recombinação
The understanding of the central mechanisms favouring sex and recombination in real populations is one of the fundamental issues in evolutionary biology. Based on a previous stochastic formulation to the study of sex, here we aim to investigate the conditions under which epistasis favours the fixation of the sexual mode of reproduction in a given population.
Publicado em: 2009
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2. Dependência da velocidade da catraca de Muller com fluxo de mutações benéficas : uma avaliação estocástica
Nós investigamos a evolução das populações assexuadas sujeita à ocorrência de um fluxo contínuo de mutações deletérias, onde a Catraca de Muller opera. Neste regime, a acumulação de mutações deletérias ocorre continuamente com a conseqüente perda da classe de indivíduos mais adaptados. Na nossa dissertação nós estudamos o efeito das muta
Publicado em: 2006
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3. Acúmulo de mutações em linhagens assexuadas: uma abordagem via experimentos computacionais / Accumulation of mutations in asexual lineages: a study using computer experiments
Studies about evolution have been developed since Charles Darwins publications about the Origin of species and Natural Selection in 1859. During the XX century major developments were achieved through mathematical and computational modeling, since only few number of species that their evolution can be studied in vivo, once that the time scale involed for dat
Publicado em: 2004
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4. Dinâmica adaptativa, genealogias e testes estatísticos de neutralidade em evolução molecular / Adaptive dynamics, Genealogies and statistical tests of neutrality in molecular evolution
This thesis discusses some topics of molecular evolution, extensively using generating function methods to find analytical results whenever possible. In first place, it gives the exact solution for the dynamics of an infinite population of infinitely long sequences (no back mutations) evolving under the action of deleterious mutations on either multiplicativ
Publicado em: 2004
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5. Dinâmica de modelos de genética de populações com recombinação. / Dynamics of population genetics models with recombination.
Juntamente com o processo de mutação, a recombinação intragênica, vista como a troca recíproca de material genético entre genomas, é um dos principais fatores geradores da diversidade genética. De fato, os diversos mecanismos de recombinação existentes na natureza (sexo, por exemplo) são freqüentemente citados como invenções do processo de evo
Publicado em: 2003
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6. Rapid fitness losses in mammalian RNA virus clones due to Muller's ratchet.
Muller's ratchet is an important concept in population genetics. It predicts that when mutation rates are high and a significant proportion of mutations are deleterious, a kind of irreversible ratchet mechanism will gradually decrease the mean fitness of small populations of asexual organisms. In contrast, sexual recombination may stop or reverse this mutati
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7. Muller's Ratchet, Epistasis and Mutation Effects
In this study, computer simulation is used to show that despite synergistic epistasis for fitness, Muller's ratchet can lead to lethal fitness loss in a population of asexuals through the accumulation of deleterious mutations. This result contradicts previous work that indicated that epistasis will halt the ratchet. The present results show that epistasis wi
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8. Muller's Ratchet under Epistatic Selection
In a finite asexual population mean fitness may decrease by a process known as Muller's ratchet, which proceeds if all individuals with the minimum number of deleterious alleles are randomly lost. If these alleles have independent effects on fitness, previous analysis suggested that the rate of this decrease either remains constant or, if accumulation of mut
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9. Muller's ratchet decreases fitness of a DNA-based microbe.
Muller proposed that an asexual organism will inevitably accumulate deleterious mutations, resulting in an increase of the mutational load and an inexorable, ratchet-like, loss of the least mutated class [Muller, H.J. (1964) Mutat. Res. 1, 2-9]. The operation of Muller's ratchet on real populations has been experimentally demonstrated only in RNA viruses. Ho
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10. The Advantage of Sex in the RNA Virus φ6
When laboratory populations of the RNA bacteriophage φ6 are subjected to intensified genetic drift, they experience a decline in fitness. These experiments demonstrate that the average effect of mutations is deleterious, and they are used to suggest that Muller's ratchet can operate in these viruses. However, the operation of Muller's ratchet does not alone
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11. Drastic Fitness Loss in Human Immunodeficiency Virus Type 1 upon Serial Bottleneck Events
Muller’s ratchet predicts fitness losses in small populations of asexual organisms because of the irreversible accumulation of deleterious mutations and genetic drift. This effect should be enhanced if population bottlenecks intervene and fixation of mutations is not compensated by recombination. To study whether Muller’s ratchet could operate in a retro
American Society for Microbiology.
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12. Many-trillionfold amplification of single RNA virus particles fails to overcome the Muller's ratchet effect.
We showed earlier that transfers of large populations of RNA viruses lead to fitness gains and that repeated genetic bottleneck transfers result in fitness losses due to Muller's ratchet. In the present study, we examined the effects of genetic bottleneck passages intervening between population passages, a process akin to some natural viral transmissions, us