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‣ Variação fenotípica de Batrachochytrium dendrobatidis como preditora de infecção em anuros da Mata Atlântica; Local phenotypic variation in amphibian-killing fungus predicts

Carolina Lambertini
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 12/08/2014 Português
Relevância na Pesquisa
67.34103%
Os anfíbios são os animais mais ameaçados do planeta, tendo como fatores mais impactantes a perda de habitat e a quitridiomicose. Esta doença em anuros é causada pelo fungo Batrachochytrium dendrobatidis (Bd), que já foi registrado em todos os continentes e no Brasil estende-se por toda a Mata Atlântica, e já foi encontrado no Cerrado e na Amazônia. Existem diversos fatores que podem influenciar a dinâmica de infecção na natureza, e como fatores intrínsecos ao Bd podemos citar a variação genotípica, morfológica, variação na virulência e taxas de crescimento. Com isso, o presente estudo teve como objetivos realizar a caracterização genotípica e fenotípica de cepas de Bd provenientes de um gradiente de elevação na Mata Atlântica, e verificar se existem associações entre o tamanho dos zoósporos e zoosporângios das cepas isoladas com dados de prevalência e intensidade de infecção e taxa de crescimento do Bd. Adicionalmente, foi analisado se as taxas de infecção aumentam conforme o aumento da elevação. Para tanto, foram isoladas e genotipadas cinco cepas de Bd. Foi realizado o diagnóstico e quantificação da doença, assim como a confecção de suas curvas de crescimento. Com base nos resultados foram desenvolvidos dois índices relacionados à variação em tamanho e dados de prevalência e intensidade de infecção. Todas as cepas isoladas pertencem à linhagem Bd-GPL2. Foi detectada variação fenotípica entre as cepas e associações entre tamanho das cepas com prevalência e intensidade de infecção...

‣ Extensive Phenotypic Variation in Early Flowering Mutants of Arabidopsis1

Pouteau, Sylvie; Ferret, Valérie; Gaudin, Valérie; Lefebvre, Delphine; Sabar, Mohammed; Zhao, Gengchun; Prunus, Franck
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /05/2004 Português
Relevância na Pesquisa
47.515054%
Flowering time, the major regulatory transition of plant sequential development, is modulated by multiple endogenous and environmental factors. By phenotypic profiling of 80 early flowering mutants of Arabidopsis, we examine how mutational reduction of floral repression is associated with changes in phenotypic plasticity and stability. Flowering time measurements in mutants reveal deviations from the linear relationship between the number of leaves and number of days to bolting described for natural accessions and late flowering mutants. The deviations correspond to relative early bolting and relative late bolting phenotypes. Only a minority of mutants presents no detectable phenotypic variation. Mutants are characterized by a broad release of morphological pleiotropy under short days, with leaf characters being most variable. They also exhibit changes in phenotypic plasticity across environments for florigenic-related responses, including the reaction to light and dark, photoperiodic behavior, and Suc sensitivity. Morphological pleiotropy and plasticity modifications are differentially distributed among mutants, resulting in a large diversity of multiple phenotypic changes. The pleiotropic effects observed may indicate that floral repression defects are linked to global developmental perturbations. This first...

‣ Genetic interactions between [PSI+] and nonstop mRNA decay affect phenotypic variation

Wilson, Marenda A.; Meaux, Stacie; Parker, Roy; van Hoof, Ambro
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
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47.64216%
Yeast strains can reversibly interconvert between [PSI+] and [psi-] states. The [PSI+] state is caused by a prion form of the translation termination factor eRF3. The [PSI+] state causes read-through at stop codons and can lead to phenotypic variation, although the molecular mechanisms causing those phenotypic changes remain unknown. We identify an interaction between [PSI+]-induced phenotypic variation and defects in nonstop mRNA decay. Nonstop mRNA decay is triggered when a ribosome reaches the 3′ end of the transcript. In contrast, we observed little interaction between [PSI+]-induced phenotypic variation and defects in nonsense-mediated decay, which lead to suppression of premature stop codons. These results suggest that at least some of the phenotypic effects of [PSI+] may be due to read-through of “normal” stop codons, thereby producing extended proteins. Moreover, these observations suggest that nonstop mRNA decay may limit [PSI+]-induced phenotypic variation. Such a process would allow periodic sampling of the 3′ UTR, which can diverge rapidly, for novel and beneficial protein extensions.

‣ The tRNA-Tyr gene family of Saccharomyces cerevisiae: agents of phenotypic variation and position effects on mutation frequency.

Ito-Harashima, Sayoko; Hartzog, Phillip E; Sinha, Himanshu; McCusker, John H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/2002 Português
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Extensive phenotypic diversity or variation exists in clonal populations of microorganisms and is thought to play a role in adaptation to novel environments. This phenotypic variation or instability, which occurs by multiple mechanisms, may be a form of cellular differentiation and a stochastic means for modulating gene expression. This work dissects a case of phenotypic variation in a clinically derived Saccharomyces cerevisiae strain involving a cox15 ochre mutation, which acts as a reporter. The ochre mutation reverts to sense at a low frequency while tRNA-Tyr ochre suppressors (SUP-o) arise at a very high frequency to produce this phenotypic variation. The SUP-o mutations are highly pleiotropic. In addition, although all SUP-o mutations within the eight-member tRNA-Tyr gene family suppress the ochre mutation reporter, there are considerable phenotypic differences among the different SUP-o mutants. Finally, and of particular interest, there is a strong position effect on mutation frequency within the eight-member tRNA-Tyr gene family, with one locus, SUP6, mutating at a much higher than average frequency and two other loci, SUP2 and SUP8, mutating at much lower than average frequencies. Mechanisms for the position effect on mutation frequency are evaluated.

‣ Genetics, phosphorus availability, and herbivore-derived induction as sources of phenotypic variation of leaf volatile terpenes in a pine species

Sampedro, Luis; Moreira, Xoaquín; Llusia, Joan; Peñuelas, Josep; Zas, Rafael
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em /10/2010 Português
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47.52791%
Oleoresin produced and stored in pine tree leaves provides direct resistance to herbivores, while leaf volatile terpenes (LVT) in the resin are also powerful airborne infochemicals. Resin concentration and profile show considerable spatial and temporal phenotypic variation within and among pine populations. LVT biochemistry is known to be under genetic control, and although LVT should be plastic to diverse abiotic and biotic environmental factors such as nutrient availability and herbivore attack, little is known about their relative contributions and interactive effects. The aim of this paper was to clarify whether reduced phosphorus availability could increase the LVT concentration and affect the expression of herbivore-derived induced defences, and how plasticity would contribute to the phenotypic variation of LVT. The constitutive and methyl-jasmonate (MeJa) induced LVT concentration and profile were analysed in 17 half-sib Pinus pinaster families growing under two levels of P-availability (complete and P-limited fertilization). Individual terpene concentrations showed large additive genetic variation, which was more pronounced in the control than in MeJa-induced pines. MeJa application did not affect the LVT concentration, but significantly modified the LVT profile by depleting the α-pinene content and reducing the sesquiterpene fraction. Low P-availability strongly reduced plant growth and foliar nutrient concentrations...

‣ Evolution of adaptive phenotypic variation patterns by direct selection for evolvability

Pavlicev, Mihaela; Cheverud, James M.; Wagner, Günter P.
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Português
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47.555938%
A basic assumption of the Darwinian theory of evolution is that heritable variation arises randomly. In this context, randomness means that mutations arise irrespective of the current adaptive needs imposed by the environment. It is broadly accepted, however, that phenotypic variation is not uniformly distributed among phenotypic traits, some traits tend to covary, while others vary independently, and again others barely vary at all. Furthermore, it is well established that patterns of trait variation differ among species. Specifically, traits that serve different functions tend to be less correlated, as for instance forelimbs and hind limbs in bats and humans, compared with the limbs of quadrupedal mammals. Recently, a novel class of genetic elements has been identified in mouse gene-mapping studies that modify correlations among quantitative traits. These loci are called relationship loci, or relationship Quantitative Trait Loci (rQTL), and affect trait correlations by changing the expression of the existing genetic variation through gene interaction. Here, we present a population genetic model of how natural selection acts on rQTL. Contrary to the usual neo-Darwinian theory, in this model, new heritable phenotypic variation is produced along the selected dimension in response to directional selection. The results predict that selection on rQTL leads to higher correlations among traits that are simultaneously under directional selection. On the other hand...

‣ Identification of Genomic Regions Associated with Phenotypic Variation between Dog Breeds using Selection Mapping

Vaysse, Amaury; Ratnakumar, Abhirami; Derrien, Thomas; Axelsson, Erik; Rosengren Pielberg, Gerli; Sigurdsson, Snaevar; Fall, Tove; Seppälä, Eija H.; Hansen, Mark S. T.; Lawley, Cindy T.; Karlsson, Elinor K.; ; Bannasch, Danika; Vilà, Carles; Lohi, Hann
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.49084%
The extraordinary phenotypic diversity of dog breeds has been sculpted by a unique population history accompanied by selection for novel and desirable traits. Here we perform a comprehensive analysis using multiple test statistics to identify regions under selection in 509 dogs from 46 diverse breeds using a newly developed high-density genotyping array consisting of >170,000 evenly spaced SNPs. We first identify 44 genomic regions exhibiting extreme differentiation across multiple breeds. Genetic variation in these regions correlates with variation in several phenotypic traits that vary between breeds, and we identify novel associations with both morphological and behavioral traits. We next scan the genome for signatures of selective sweeps in single breeds, characterized by long regions of reduced heterozygosity and fixation of extended haplotypes. These scans identify hundreds of regions, including 22 blocks of homozygosity longer than one megabase in certain breeds. Candidate selection loci are strongly enriched for developmental genes. We chose one highly differentiated region, associated with body size and ear morphology, and characterized it using high-throughput sequencing to provide a list of variants that may directly affect these traits. This study provides a catalogue of genomic regions showing extreme reduction in genetic variation or population differentiation in dogs...

‣ Factors other than genotype account largely for the phenotypic variation of the pulmonary valve in Syrian hamsters

Carmen Fernández, M; Durán, Ana C; Fernández, Borja; Arqué, Josep M; Anderson, Robert H; Sans-Coma, Valentín
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Português
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47.49084%
Understanding of the aetiology of congenitally anomalous pulmonary valves remains incomplete. The aim of our study, therefore, was to elucidate the degree to which the phenotypic variation known to exist for the pulmonary valve relies on genotypic variation. Initially, we tested the hypothesis that genetically alike individuals would display similar valvar phenotypes if the phenotypic arrangement depended entirely, or almost entirely, on the genotype. Thus, we examined pulmonary valves from 982 Syrian hamsters belonging to two families subject to systematic inbreeding by crossing siblings. Their coefficient of inbreeding was 0.999 or higher, so they could be considered genetically alike. External environmental factors were standardized as much as possible. A further 97 Syrian hamsters from an outbred colony were used for comparative purposes. In both the inbred and outbred hamsters, we found valves with a purely trifoliate, or tricuspid, design, trifoliate valves with a more or less extensive fusion of the right and left leaflets, bifoliate, or bicuspid, valves with fused right and left leaflets, with or without a raphe located in the conjoined arterial sinus, and quadrifoliate, or quadricuspid, valves. The incidence of the different valvar morphological variants was similar in the outbred and inbred colonies...

‣ Stressful environments induce novel phenotypic variation: hierarchical reaction norms for sperm performance of a pervasive invader

Purchase, Craig F; Moreau, Darek T R
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Português
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47.52791%
Genetic variation for phenotypic plasticity is ubiquitous and important. However, the scale of such variation including the relative variability present in reaction norms among different hierarchies of biological organization (e.g., individuals, populations, and closely related species) is unknown. Complicating interpretation is a trade-off in environmental scale. As plasticity can only be inferred over the range of environments tested, experiments focusing on fine tuned responses to normal or benign conditions may miss cryptic phenotypic variation expressed under novel or stressful environments. Here, we sought to discern the presence and shape of plasticity in the performance of brown trout sperm as a function of optimal to extremely stressful river pH, and demarcate if the reaction norm varies among genotypes. Our overarching goal was to determine if deteriorating environmental quality increases expressed variation among individuals. A more applied aim was to ascertain whether maintaining sperm performance over a wide pH range could help explain how brown trout are able to invade diverse river systems when transplanted outside of their native range. Individuals differed in their reaction norms of phenotypic expression of an important trait in response to environmental change. Cryptic variation was revealed under stressful conditions...

‣ Earlier Migration Timing, Decreasing Phenotypic Variation, and Biocomplexity in Multiple Salmonid Species

Kovach, Ryan P.; Joyce, John E.; Echave, Jesse D.; Lindberg, Mark S.; Tallmon, David A.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 10/01/2013 Português
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47.55755%
Climate-induced phenological shifts can influence population, evolutionary, and ecological dynamics, but our understanding of these phenomena is hampered by a lack of long-term demographic data. We use a multi-decade census of 5 salmonid species representing 14 life histories in a warming Alaskan stream to address the following key questions about climate change and phenology: How consistent are temporal patterns and drivers of phenology for similar species and alternative life histories? Are shifts in phenology associated with changes in phenotypic variation? How do phenological changes influence the availability of resource subsidies? For most salmonid species, life stages, and life histories, freshwater temperature influences migration timing – migration events are occurring earlier in time (mean = 1.7 days earlier per decade over the 3–5 decades), and the number of days over which migration events occur is decreasing (mean = 1.5 days per decade). Temporal trends in migration timing were not correlated with changes in intra-annual phenotypic variation, suggesting that these components of the phenotypic distribution have responded to environmental change independently. Despite commonalities across species and life histories...

‣ Rapid Plant Invasion in Distinct Climates Involves Different Sources of Phenotypic Variation

Monty, Arnaud; Bizoux, Jean-Philippe; Escarré, José; Mahy, Grégory
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 30/01/2013 Português
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47.70726%
When exotic species spread over novel environments, their phenotype will depend on a combination of different processes, including phenotypic plasticity (PP), local adaptation (LA), environmental maternal effects (EME) and genetic drift (GD). Few attempts have been made to simultaneously address the importance of those processes in plant invasion. The present study uses the well-documented invasion history of Senecio inaequidens (Asteraceae) in southern France, where it was introduced at a single wool-processing site. It gradually invaded the Mediterranean coast and the Pyrenean Mountains, which have noticeably different climates. We used seeds from Pyrenean and Mediterranean populations, as well as populations from the first introduction area, to explore the phenotypic variation related to climatic variation. A reciprocal sowing experiment was performed with gardens under Mediterranean and Pyrenean climates. We analyzed climatic phenotypic variation in germination, growth, reproduction, leaf physiology and survival. Genetic structure in the studied invasion area was characterized using AFLP. We found consistent genetic differentiation in growth traits but no home-site advantage, so weak support for LA to climate. In contrast, genetic differentiation showed a relationship with colonization history. PP in response to climate was observed for most traits...

‣ Phenotypic Variation in the Plant Pathogenic Bacterium Acidovorax citrulli

Shrestha, Ram Kumar; Rosenberg, Tally; Makarovsky, Daria; Eckshtain-Levi, Noam; Zelinger, Einat; Kopelowitz, June; Sikorski, Johannes; Burdman, Saul
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 02/09/2013 Português
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47.50622%
Acidovorax citrulli causes bacterial fruit blotch (BFB) of cucurbits, a disease that threatens the cucurbit industry worldwide. Despite the economic importance of BFB, little is known about pathogenicity and fitness strategies of the bacterium. We have observed the phenomenon of phenotypic variation in A. citrulli. Here we report the characterization of phenotypic variants (PVs) of two strains, M6 and 7a1, isolated from melon and watermelon, respectively. Phenotypic variation was observed following growth in rich medium, as well as upon isolation of bacteria from inoculated plants or exposure to several stresses, including heat, salt and acidic conditions. When grown on nutrient agar, all PV colonies possessed a translucent appearance, in contrast to parental strain colonies that were opaque. After 72 h, PV colonies were bigger than parental colonies, and had a fuzzy appearance relative to parental strain colonies that are relatively smooth. A. citrulli colonies are generally surrounded by haloes detectable by the naked eye. These haloes are formed by type IV pilus (T4P)-mediated twitching motility that occurs at the edge of the colony. No twitching haloes could be detected around colonies of both M6 and 7a1 PVs, and microscopy observations confirmed that indeed the PVs did not perform twitching motility. In agreement with these results...

‣ Relative contribution of additive, dominance and imprinting effects to phenotypic variation in body size and growth between divergent selection lines of mice

Hager, Reinmar; Cheverud, James M.; Wolf, Jason B.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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47.52791%
Epigenetic effects attributed to genomic imprinting are increasingly recognized as an important source of variation in quantitative traits. However, little is known about their relative contribution to phenotypic variation compared to those of additive and dominance effects, and almost nothing about their role in phenotypic evolution. Here we address these questions by investigating the relative contribution of additive, dominance and imprinting effects of quantitative trait loci (QTL) to variation in ‘early’ and ‘late’ body weight in an intercross of mice selected for divergent adult body weight. We identified 18 loci on 13 chromosomes; additive effects accounted for most of the phenotypic variation throughout development, and imprinting effects were always small. Genetic effects on early weight showed more dominance, less additive and, surprisingly, less imprinting variation than that of late weight. The predominance of additivity of QTL effects on body weight follows the expectation that additive effects account for the evolutionary divergence between selection lines. We hypothesize that the appearance of more imprinting effects on late body weight may be a consequence of divergent selection on adult body weight, which may have indirectly selected for alleles showing partial imprinting effects due to their associated additive effects...

‣ Intraspecific phenotypic variation in a fish predator affects multitrophic lake metacommunity structure

Howeth, Jennifer G; Weis, Jerome J; Brodersen, Jakob; Hatton, Elizabeth C; Post, David M
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
47.49703%
Contemporary insights from evolutionary ecology suggest that population divergence in ecologically important traits within predators can generate diversifying ecological selection on local community structure. Many studies acknowledging these effects of intraspecific variation assume that local populations are situated in communities that are unconnected to similar communities within a shared region. Recent work from metacommunity ecology suggests that species dispersal among communities can also influence species diversity and composition but can depend upon the relative importance of the local environment. Here, we study the relative effects of intraspecific phenotypic variation in a fish predator and spatial processes related to plankton species dispersal on multitrophic lake plankton metacommunity structure. Intraspecific diversification in foraging traits and residence time of the planktivorous fish alewife (Alosa pseudoharengus) among coastal lakes yields lake metacommunities supporting three lake types which differ in the phenotype and incidence of alewife: lakes with anadromous, landlocked, or no alewives. In coastal lakes, plankton community composition was attributed to dispersal versus local environmental predictors, including intraspecific variation in alewives. Local and beta diversity of zooplankton and phytoplankton was additionally measured in response to intraspecific variation in alewives. Zooplankton communities were structured by species sorting...

‣ Epigenetics and phenotypic variation in mammals

Peaston, Anne E.; Whitelaw, Emma
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Publicado em //2006 Português
Relevância na Pesquisa
47.62265%
What causes phenotypic variation? By now it is clear that phenotype is a result of the interaction between genotype and environment, in addition to variation not readily attributable to either. Epigenetic phenomena associated with phenotypic variation at the biochemical, cellular, tissue, and organism level are now well recognized and are likely to contribute to the “intangible variation” alluded to. While it is clear that epigenetic modifications are mitotically heritable, the fidelity of this process is not well understood. Inheritance through more than one generation of meioses is even less well studied. So it remains unclear to what extent epigenetic changes contribute to phenotypic variation in natural populations. How might such evidence be obtained? What are the features of phenotypes that might suggest an epigenetic component? How much of the epigenetic component is truly independent of genetic changes? The answers to such questions must come from studies designed specifically to detect subtle, stochastically determined phenotypic variation in suitable animal models.

‣ Phenotypic Variation in Infants, Not Adults, Reflects Genotypic Variation among Chimpanzees and Bonobos

Morimoto, Naoki; Ponce de León, Marcia S.; Zollikofer, Christoph P. E.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 11/07/2014 Português
Relevância na Pesquisa
47.64216%
Studies comparing phenotypic variation with neutral genetic variation in modern humans have shown that genetic drift is a main factor of evolutionary diversification among populations. The genetic population history of our closest living relatives, the chimpanzees and bonobos, is now equally well documented, but phenotypic variation among these taxa remains relatively unexplored, and phenotype-genotype correlations are not yet documented. Also, while the adult phenotype is typically used as a reference, it remains to be investigated how phenotype-genotye correlations change during development. Here we address these questions by analyzing phenotypic evolutionary and developmental diversification in the species and subspecies of the genus Pan. Our analyses focus on the morphology of the femoral diaphysis, which represents a functionally constrained element of the locomotor system. Results show that during infancy phenotypic distances between taxa are largely congruent with non-coding (neutral) genotypic distances. Later during ontogeny, however, phenotypic distances deviate from genotypic distances, mainly as an effect of heterochronic shifts between taxon-specific developmental programs. Early phenotypic differences between Pan taxa are thus likely brought about by genetic drift while late differences reflect taxon-specific adaptations.

‣ Epigenetics and phenotypic variation in mammals

Peaston, A.; Whitelaw, E.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2006 Português
Relevância na Pesquisa
47.59462%
What causes phenotypic variation? By now it is clear that phenotype is a result of the interaction between genotype and environment, in addition to variation not readily attributable to either. Epigenetic phenomena associated with phenotypic variation at the biochemical, cellular, tissue, and organism level are now well recognized and are likely to contribute to the ‘‘intangible variation’’ alluded to. While it is clear that epigenetic modifications are mitotically heritable, the fidelity of this process is not well understood. Inheritance through more than one generation of meioses is even less well studied. So it remains unclear to what extent epigenetic changes contribute to phenotypic variation in natural populations. How might such evidence be obtained? What are the features of phenotypes that might suggest an epigenetic component? How much of the epigenetic component is truly independent of genetic changes? The answers to such questions must come from studies designed specifically to detect subtle, stochastically determined phenotypic variation in suitable animal models.; Anne E. Peaston and Emma Whitelaw

‣ Genetic and environmental modulation of phenotypic variation in Arabidopsis thaliana; Genetische und ökologische Modulation der phänotypischen Variation in Arabidopsis thaliana

Sureshkumar, Sridevi
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
Português
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67.59551%
Natural phenotypic variation allows us to explore adaptation and the genetic architecture. In this study we had demonstrated that allelic variation in the photoreceptor PHYTOCHROME C (PHYC) contributes to flowering and light responses in natural populations of Arabidopsis thaliana. Our work coupled with earlier work on other light receptors shows that the photoreceptor family to be highly variable and adaptive in plants. In second part of the research we reveal hidden genetic variation and its phenotypic consequences, using Arabidopsis thaliana wild strains. At higher temperature one of the strain (Bur-0) displayed a conditional leaf morphological defect and growth arrest. Through linkage analysis we identified the gene encoding ISOPROPYLMALATE ISOMERASE LARGE SUBUNIT 1 (IIL1) involved in amino acid biosynthesis to be carrying a TTC/GAA triplet repeat expansion in the intronic region, which is responsible for the growth arrest phenotype. Plants carrying induced or spontaneous deletions in the expansion appear normal at higher temperatures. Our findings reveal striking parallels to the human genetic disease Fredereich ataxia (FRDA), a neuronal disease caused by an intronic GAA/TTC triplet expansion thereby providing an excellent experimentally amenable genetic model to study fundamental aspects of triplet expansions associated genetic diseases.; Natürliche phänotypischen Variation ermöglicht es uns...

‣ Genetic and epigenetic regulation of the cell wall glycoproteins, Flo10p and Flo11p, generate phenotypic variation in S. cerevisiae

Halme, Adrian Jones, 1971-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 275 leaves; 12505340 bytes; 12505139 bytes; application/pdf; application/pdf
Português
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Many organisms, in response to selective pressures imposed by their environment, have evolved mechanisms that allow them to generate phenotypic variation. Such phenotypic variation can result from genetic regulation, in which changes in DNA sequence produce the variant phenotype, or epigenetic regulation, in which there are no changes in DNA sequence associated with the variant phenotype. This doctoral thesis describes the identification and analysis of novel phenotypic variation among populations of the bakers' yeast, Saccharomyces cerevisiae. This phenotypic variation, most easily identified as a switching between smooth and wrinkled colony morphologies, involves changes in several adhesive and morphological phenotypes. Experiments reveal that this phenotypic switch is the result of both genetic and epigenetic regulation. The genetic component of this phenotypic variation involves mutation at either of the two yeast Ras-GAP encoding genes, IRA] and IRA2. The IRA genes are hot spots for mutation, as loss-of-function mutations at these genes are much more frequent than mutations at other loci (- 10-6). Several factors regulate the genetic stability of these genes, including DNA double-strand break (DSB) repair pathways. Genetic analysis demonstrates that both homologous recombination (HR) and non-homologous end-joining (NHEJ) pathways of DSB repair maintain genetic stability at the IRA loci. Since these pathways specifically process a DSB substrate...

‣ Estructura genética poblacional, historia demográfica y variación fenotípica del róbalo, Eleginops maclovinus (Perciformes); Geographic genetic structure, demographic history and phenotypic variation of the Patagonian blenny Eleginops maclovinus

Ceballos, Santiago Guillermo
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2011 Português
Relevância na Pesquisa
47.605728%
Para comprender los fenómenos involucrados en la evolución de las especies es importante estudiar los patrones de variación geográfica de los atributos genéticos y fenotípicos de las poblaciones. El presente trabajo analiza la estructura genética y la variación fenotípica en el pez marino, Eleginops maclovinus (róbalo), una especie endémica del sur de Sudamérica que constituye uno de los recursos marinos costeros de mayor importancia socioeconómica de la región. El estudio genético se realizó con individuos colectados a lo largo de casi todo el rango latitudinal de la especie en la costa atlántica y pacífica. Se obtuvieron secuencias parciales del gen mitocondrial citocromo b de un total de 261 individuos provenientes de 9 localidades y también se analizaron 9 loci de microsatélites en 239 individuos provenientes de 5 localidades. El estudio de la variación fenotípica se realizó mediante morfometría geométrica en 140 individuos provenientes de 4 localidades ubicadas a lo largo de la costa atlántica. El ADN mitocondrial reveló un patrón general de baja estructuración poblacional y una clara señal de expansión demográfica ocurrida, probablemente, durante el Pleistoceno Medio. El análisis de microsatélites sugirió la existencia de dos grupos genéticos...