Página 9 dos resultados de 7455 itens digitais encontrados em 0.016 segundos

‣ Brain development and predation: plastic responses depend on evolutionary history

Gonda, Abigél; Välimäki, Kaisa; Herczeg, Gábor; Merilä, Juha
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.73105%
Although the brain is known to be a very plastic organ, the effects of common ecological interactions like predation or competition on brain development have remained largely unexplored. We reared nine-spined sticklebacks (Pungitius pungitius) from two coastal marine (predation-adapted) and two isolated pond (competition-adapted) populations in a factorial experiment, manipulating perceived predatory risk and food supply to see (i) if the treatments affected brain development and (ii) if there was population differentiation in the response to treatments. We detected differences in plasticity of the bulbus olfactorius (chemosensory centre) between habitats: marine fish were not plastic, whereas pond fish had larger bulbi olfactorii in the presence of perceived predation. Marine fish had larger bulbus olfactorius overall. Irrespective of population origin, the hypothalamus was smaller in the presence of perceived predatory risk. Our results demonstrate that perceived predation risk can influence brain development, and that the effect of an environmental factor on brain development may depend on the evolutionary history of a given population in respect to this environmental factor.

‣ Evolutionary principles of modular gene regulation in yeasts

Thompson, Dawn A; Roy, Sushmita; Chan, Michelle; Styczynsky, Mark P; Pfiffner, Jenna; French, Courtney; Socha, Amanda; Thielke, Anne; Napolitano, Sara; Muller, Paul; Kellis, Manolis; Konieczka, Jay H; Wapinski, Ilan; Regev, Aviv
Fonte: eLife Sciences Publications, Ltd Publicador: eLife Sciences Publications, Ltd
Tipo: Artigo de Revista Científica
Publicado em 18/06/2013 Português
Relevância na Pesquisa
46.73105%
Divergence in gene regulation can play a major role in evolution. Here, we used a phylogenetic framework to measure mRNA profiles in 15 yeast species from the phylum Ascomycota and reconstruct the evolution of their modular regulatory programs along a time course of growth on glucose over 300 million years. We found that modules have diverged proportionally to phylogenetic distance, with prominent changes in gene regulation accompanying changes in lifestyle and ploidy, especially in carbon metabolism. Paralogs have significantly contributed to regulatory divergence, typically within a very short window from their duplication. Paralogs from a whole genome duplication (WGD) event have a uniquely substantial contribution that extends over a longer span. Similar patterns occur when considering the evolution of the heat shock regulatory program measured in eight of the species, suggesting that these are general evolutionary principles.

‣ Evolutionary dynamics of cancer in response to targeted combination therapy

Bozic, Ivana; Reiter, Johannes G; Allen, Benjamin; Antal, Tibor; Chatterjee, Krishnendu; Shah, Preya; Moon, Yo Sup; Yaqubie, Amin; Kelly, Nicole; Le, Dung T; Lipson, Evan J; Chapman, Paul B; Diaz, Luis A; Vogelstein, Bert; Nowak, Martin A
Fonte: eLife Sciences Publications, Ltd Publicador: eLife Sciences Publications, Ltd
Tipo: Artigo de Revista Científica
Publicado em 25/06/2013 Português
Relevância na Pesquisa
46.73105%
In solid tumors, targeted treatments can lead to dramatic regressions, but responses are often short-lived because resistant cancer cells arise. The major strategy proposed for overcoming resistance is combination therapy. We present a mathematical model describing the evolutionary dynamics of lesions in response to treatment. We first studied 20 melanoma patients receiving vemurafenib. We then applied our model to an independent set of pancreatic, colorectal, and melanoma cancer patients with metastatic disease. We find that dual therapy results in long-term disease control for most patients, if there are no single mutations that cause cross-resistance to both drugs; in patients with large disease burden, triple therapy is needed. We also find that simultaneous therapy with two drugs is much more effective than sequential therapy. Our results provide realistic expectations for the efficacy of new drug combinations and inform the design of trials for new cancer therapeutics.

‣ Genome-wide evolutionary response to a heat wave in Drosophila

Rodríguez-Trelles, Francisco; Tarrío, Rosa; Santos, Mauro
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Publicado em 23/08/2013 Português
Relevância na Pesquisa
46.73105%
Extreme climatic events can substantially affect organismal performance and Darwinian fitness. In April 2011, a strong heat wave struck extensive geographical areas of the world, including Western Europe. At that time, we happened to resume and extend a long-term time series of seasonal genetic data in the widespread fly Drosophila subobscura, which provided a unique opportunity to quantify the intensity of the genetic perturbation caused by the heat wave. We show that the spring 2011 genetic constitution of the populations transiently shifted to summer-like frequencies, and that the magnitude of the genetic anomaly quantitatively matched the temperature anomaly. The results provide compelling evidence that direct effects of rising temperature are driving adaptive evolutionary shifts, and also suggest a strong genetic resilience in this species.

‣ Non-allelic gene conversion enables rapid evolutionary change at multiple regulatory sites encoded by transposable elements

Ellison, Christopher E; Bachtrog, Doris
Fonte: eLife Sciences Publications, Ltd Publicador: eLife Sciences Publications, Ltd
Tipo: Artigo de Revista Científica
Publicado em 17/02/2015 Português
Relevância na Pesquisa
46.73105%
Transposable elements (TEs) allow rewiring of regulatory networks, and the recent amplification of the ISX element dispersed 77 functional but suboptimal binding sites for the dosage compensation complex to a newly formed X chromosome in Drosophila. Here we identify two linked refining mutations within ISX that interact epistatically to increase binding affinity to the dosage compensation complex. Selection has increased the frequency of this derived haplotype in the population, which is fixed at 30% of ISX insertions and polymorphic among another 41%. Sharing of this haplotype indicates that high levels of gene conversion among ISX elements allow them to ‘crowd-source’ refining mutations, and a refining mutation that occurs at any single ISX element can spread in two dimensions: horizontally across insertion sites by non-allelic gene conversion, and vertically through the population by natural selection. These results describe a novel route by which fully functional regulatory elements can arise rapidly from TEs and implicate non-allelic gene conversion as having an important role in accelerating the evolutionary fine-tuning of regulatory networks.

‣ Experimental evolution reveals hidden diversity in evolutionary pathways

Lind, Peter A; Farr, Andrew D; Rainey, Paul B
Fonte: eLife Sciences Publications, Ltd Publicador: eLife Sciences Publications, Ltd
Tipo: Artigo de Revista Científica
Publicado em 25/03/2015 Português
Relevância na Pesquisa
46.73105%
Replicate populations of natural and experimental organisms often show evidence of parallel genetic evolution, but the causes are unclear. The wrinkly spreader morph of Pseudomonas fluorescens arises repeatedly during experimental evolution. The mutational causes reside exclusively within three pathways. By eliminating these, 13 new mutational pathways were discovered with the newly arising WS types having fitnesses similar to those arising from the commonly passaged routes. Our findings show that parallel genetic evolution is strongly biased by constraints and we reveal the genetic bases. From such knowledge, and in instances where new phenotypes arise via gene activation, we suggest a set of principles: evolution proceeds firstly via pathways subject to negative regulation, then via promoter mutations and gene fusions, and finally via activation by intragenic gain-of-function mutations. These principles inform evolutionary forecasting and have relevance to interpreting the diverse array of mutations associated with clinically identical instances of disease in humans.

‣ The genetic demography history and phylogeography of the Andean bear (Tremarctos ornatus; Ursidae) by means of microsatellites and mtDNA markers.; Molecular Population Genetics, Evolutionary Biology, and Biological Conservation of Neotropical Carnivores

Ruiz-García, Manuel
Fonte: Nova Science Publishers, Inc. Publicador: Nova Science Publishers, Inc.
Formato: 129-158
Português
Relevância na Pesquisa
46.73105%
Herein I show new molecular data (microsatellites and mtDNA sequences) for the Andean bear based on a larger sample size (286 individuals) than previously analyzed by Ruiz-García (2003, 2007) and Ruiz-García et al., (2003, 2005). This sample was composed of individuals obtained in Venezuela, Colombia, Ecuador, Peru and Bolivia. Four main results came out of this study. 1- The evolutionary microsatellite dynamics of the markers applied to the spectacled bear revealed 20% of multiple-step mutations and an overall historical effective number of around 10,000 individuals; 2- Microsatellites detected a significant genetic heterogeneity for a large fraction of the comparisons made among the different populations considered, although this genetic differentiation was smaller than that obtained in previous studies; 3- No tests detected any significant bottleneck event in the history of the overall population nor in the spectacled bear populations of Colombia and Ecuador. In contrast, some tests detected historical population expansions in this species. This was contrasted with the possible climatic changes during the late Pleistocene. 4- The phylogeographic analysis by means of the mitochondrial control region sequences showed, in contrast to the microsatellites...

‣ Phylogeography and conservation biology of the Purple-crowned Fairy-wren, Malurus coronatus

Skroblin, Anja
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
Português
Relevância na Pesquisa
46.71941%
The purple-crowned fairy-wren (Malurus coronatus) is a declining passerine that is restricted to the dense patches of vegetation that grow along waterways in the wet-dry tropics of northern Australia. The species is threatened by ongoing degradation of riparian habitat caused by the grazing and trampling of introduced herbivores, intense fires and weed incursion. Although the western subspecies (Malurus coronatus coronatus) has been listed as endangered, conservation has been hampered by poor information regarding its distribution and what factors influence its fine-scale occurrence. This thesis aims to rectify these knowledge gaps and produce recommendations for management goals that could improve the conservation of M. c. coronatus, its riparian habitat, and other vulnerable species within the habitat. To validate the use of M. c. coronatus as a separate unit for conservation, we firstly affirmed the genetic and thus evolutionary distinctiveness of the morphologically defined subspecies of purple-crowned fairy-wren (M. c. coronatus and Malurus coronatus macgillivrayi). Because M. c. coronatus was of greater conservation concern it became the focus of the subsequent chapters. Extensive aerial and ground surveys, accompanied by an analysis of population genetics...

‣ Understanding Randomness and its Impact on Student Learning: Lessons Learned from Building the Biology Concept Inventory (BCI)

Garvin-Doxas, Kathy; Klymkowsky, Michael W.
Fonte: American Society for Cell Biology Publicador: American Society for Cell Biology
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
Relevância na Pesquisa
46.801924%
While researching student assumptions for the development of the Biology Concept Inventory (BCI; http://bioliteracy.net), we found that a wide class of student difficulties in molecular and evolutionary biology appears to be based on deep-seated, and often unaddressed, misconceptions about random processes. Data were based on more than 500 open-ended (primarily) college student responses, submitted online and analyzed through our Ed's Tools system, together with 28 thematic and think-aloud interviews with students, and the responses of students in introductory and advanced courses to questions on the BCI. Students believe that random processes are inefficient, whereas biological systems are very efficient. They are therefore quick to propose their own rational explanations for various processes, from diffusion to evolution. These rational explanations almost always make recourse to a driver, e.g., natural selection in evolution or concentration gradients in molecular biology, with the process taking place only when the driver is present, and ceasing when the driver is absent. For example, most students believe that diffusion only takes place when there is a concentration gradient, and that the mutational processes that change organisms occur only in response to natural selection pressures. An understanding that random processes take place all the time and can give rise to complex and often counterintuitive behaviors is almost totally absent. Even students who have had advanced or college physics...

‣ The evolutionary origins of hierarchy

Mengistu, Henok; Huizinga, Joost; Mouret, Jean-Baptiste; Clune, Jeff
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/05/2015 Português
Relevância na Pesquisa
46.73105%
Hierarchical organization -- the recursive composition of sub-modules -- is ubiquitous in biological networks, including neural, metabolic, ecological, and genetic regulatory networks, and in human-made systems, such as large organizations and the Internet. To date, most research on hierarchy in networks has been limited to quantifying this property. However, an open, important question in evolutionary biology is why hierarchical organization evolves in the first place. It has recently been shown that modularity evolves because of the presence of a cost for network connections. Here we investigate whether such connection costs also tend to cause a hierarchical organization of such modules. In computational simulations, we find that networks without a connection cost do not evolve to be hierarchical, even when the task has a hierarchical structure. However, with a connection cost, networks evolve to be both modular and hierarchical, and these networks exhibit higher overall performance and evolvability (i.e. faster adaptation to new environments). Additional analyses confirm that hierarchy independently improves adaptability after controlling for modularity. Overall, our results suggest that the same force--the cost of connections--promotes the evolution of both hierarchy and modularity...

‣ SNP analysis reveals an evolutionary acceleration of the human-specific microRNAs

Qipeng Zhang; Ming Lu; Qinghua Cui
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Relevância na Pesquisa
46.73105%
MicroRNAs are one class of important gene regulators at the post-transcriptional level by binding to the 3’UTRs of target mRNAs. It has been reported that human microRNAs are evolutionary conserved and show lower single nucleotide polymorphisms (SNPs) than their flanking regions. However, in this study, we report that the human-specific microRNAs show a higher SNP density than both the conserved microRNAs and other control regions, suggesting rapid evolution and positive selection has occurred in these regions. Furthermore, we observe that the human-specific microRNAs show greater SNPs minor allele frequency and the SNPs in the human-specific microRNAs show fewer effects on the stability of the microRNA secondary structure, indicating that the SNPs in the human-specific microRNAs tend to be less deleterious. Finally, two microRNAs hsa-mir-423 (SNP: rs6505162), hsa-mir-608 (SNP: rs4919510) and 288 target genes that have apparently been under recent positive selection are identified. These findings will improve our understanding of the functions, evolution, and population disease susceptibility of human microRNAs.

‣ Characteristics of oligonucleotide frequencies across genomes: Conservation versus variation, strand symmetry, and evolutionary implications

Shang-Hong Zhang; Ya-Zhi Huang
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Relevância na Pesquisa
46.73105%
One of the objectives of evolutionary genomics is to reveal the genetic information contained in the primordial genome (called the primary genetic information in this paper, with the primordial genome defined here as the most primitive nucleic acid genome for earth’s life) by searching for primitive traits or relics remained in modern genomes. As the shorter a sequence is, the less probable it would be modified during genome evolution. For that reason, some characteristics of very short nucleotide sequences would have considerable chances to persist during billions of years of evolution. Consequently, conservation of certain genomic features of mononucleotides, dinucleotides, and higher-order oligonucleotides across various genomes may exist; some, if not all, of these features would be relics of the primary genetic information. Based on this assumption, we analyzed the pattern of frequencies of mononucleotides, dinucleotides, and higher-order oligonucleotides of the whole-genome sequences from 458 species (including archaea, bacteria, and eukaryotes). Also, we studied the phenomenon of strand symmetry in these genomes. The results show that the conservation of frequencies of some dinucleotides and higher-order oligonucleotides across genomes does exist...

‣ Circadian Preference and Sexual Selection: A Novel Evolutionary Approach

Davide Piffer
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Relevância na Pesquisa
46.73105%
Human sleep patterns differ across age groups and between males and females, and their association with age and gender suggest that they might have been the target of sexual selection during human evolutionary history. In this study, I will test the hypothesis that a phase-delayed circadian phase is a sexually selected trait in humans. A short version of the Horne and Ostberg questionnaire and a questionnaire on sexual behaviour were administered to 134 males and 140 females. A significant negative relationship was found between the MEQ score and the number of sexual partners among males, with evening types reporting more sexual partners than morning types. No significant relationship between females MEQ and number of sexual partners was found. Findings support the hypothesis that evening preference in males is a sexually selected trait.

‣ Eco-evolutionary consequences of road adjacency and road salt on the wood frog, Rana sylvatica

Steven P. Brady
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
46.73105%
The network of roads on the landscape is vast, and has wide-reaching ecological influence. Recent investigations have focused on understanding impacts of contaminants from road runoff, especially deicing agents such as road salt. Despite growing research concerning ecological impacts of roads, our understanding of long-term consequences remains nascent. This stems in part from a dearth of investigations, and in part because ecological research typically ignores evolution on contemporary timescales. Yet reports of evolution influencing ecological outcomes are growing, suggesting this influence may be the rule rather than the exception. This may be especially true for species with spatially structured populations. For amphibians, such structuring coupled with environmental heterogeneity has been shown to yield contemporary evolutionary responses, with rates of divergence matching that of environmental disturbance. This suggests that amphibians dwelling in roadside wetlands may evolve rapidly as a consequence of novel selection pressures, such as runoff. I evaluated this potential response using a field-based reciprocal transplant experiment. I compared growth, survival, and development of embryonic and larval wood frogs originating from five roadside and five woodland wetlands. Concomitantly...

‣ Eco-evolutionary consequences of road adjacency and road salt on the wood frog, Rana sylvatica

Steven P. Brady
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
46.73105%
The network of roads on the landscape is vast, and has wide-reaching ecological influence. Recent investigations have focused on understanding impacts of contaminants from road runoff, especially deicing agents such as road salt. Despite growing research concerning ecological impacts of roads, our understanding of long-term consequences remains nascent. This stems in part from a dearth of investigations, and in part because ecological research typically ignores evolution on contemporary timescales. Yet reports of evolution influencing ecological outcomes are growing, suggesting this influence may be the rule rather than the exception. This may be especially true for species with spatially structured populations. For amphibians, such structuring coupled with environmental heterogeneity has been shown to yield contemporary evolutionary responses, with rates of divergence matching that of environmental disturbance. This suggests that amphibians dwelling in roadside wetlands may evolve rapidly as a consequence of novel selection pressures, such as runoff. I evaluated this potential response using a field-based reciprocal transplant experiment. I compared growth, survival, and development of embryonic and larval wood frogs originating from five roadside and five woodland wetlands. Concomitantly...

‣ Circadian Preference and Sexual Selection: A Novel Evolutionary Approach

Davide Piffer
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Relevância na Pesquisa
46.73105%
Human sleep patterns differ across age groups and between males and females, and their association with age and gender suggest that they might have been the target of sexual selection during human evolutionary history. In this study, I will test the hypothesis that a phase-delayed circadian phase is a sexually selected trait in humans. A short version of the Horne and Ostberg questionnaire and a questionnaire on sexual behaviour were administered to 134 males and 140 females. A significant negative relationship was found between the MEQ score and the number of sexual partners among males, with evening types reporting more sexual partners than morning types. No significant relationship between females MEQ and number of sexual partners was found. Findings support the hypothesis that evening preference in males is a sexually selected trait.

‣ Does human imitate successful behaviors immediately?

Zhao-Jin Xu; Lian-Zhong Zhang
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Relevância na Pesquisa
46.807217%
The emergence and abundance of cooperation in animal and human societies is a challenging puzzle to evolutionary biology. Over the past decades, various mechanisms have been suggested which are capable of supporting cooperation. Imitation dynamics, however, are the most representative microscopic rules of human behaviors on studying these mechanisms. Their standard procedure is to choose the agent to imitate at random from the population. In the spatial version this means a random agent from the neighborhood. Hence, imitation rules do not include the possibility to explore the available strategies, and then they have the possibility to reach a homogeneous state rapidly when the population size is small. To prevent evolution stopping, theorists allow for random mutations in addition to the imitation dynamics. Consequently, if the microscopic rules involve both imitation and mutation, the frequency of agents switching to the more successful strategy must be higher than that of them transiting to the same target strategy via mutation dynamics. Here we show experimentally that the frequency of switching to successful strategy approximates to that of mutating to the same strategy. This suggests that imitation might play an insignificant role on the behaviors of human decision making. In addition...

‣ `The frozen accident' as an evolutionary adaptation: A rate distortion theory perspective on the dynamics and symmetries of genetic coding mechanisms

James F. Glazebrook; Rodrick Wallace
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Relevância na Pesquisa
46.73105%
We survey some interpretations and related issues concerning the frozen hypothesis due to F. Crick and how it can be explained in terms of several natural mechanisms involving error correction codes, spin glasses, symmetry breaking and the characteristic robustness of genetic networks. The approach to most of these questions involves using elements of Shannon's rate distortion theory incorporating a semantic system which is meaningful for the relevant alphabets and vocabulary implemented in transmission of the genetic code. We apply the fundamental homology between information source uncertainty with the free energy density of a thermodynamical system with respect to transcriptional regulators and the communication channels of sequence/structure in proteins. This leads to the suggestion that the frozen accident may have been a type of evolutionary adaptation.

‣ Metabolic, Replication and Genomic Category of Systems in Biology, Bioinformatics and Medicine

I. C. Baianu
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Relevância na Pesquisa
46.76732%
Metabolic-repair models, or (M,R)-systems were introduced in Relational Biology by Robert Rosen. Subsequently, Rosen represented such (M,R)-systems (or simply MRs)in terms of categories of sets, deliberately selected without any structure other than the discrete topology of sets. Theoreticians of life’s origins postulated that Life on Earth has begun with the simplest possible organism, called the primordial. Mathematicians interested in biology attempted to answer this important question of the minimal living organism by defining the functional relations that would have made life possible in such a minimal system- a grandad and grandma of all living organisms on Earth. Genomic systems are also considered as molecular realizations of (M,R)-system subcatgeories.

‣ On Asymmetry in Biology and Nature

I. C. Baianu
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
Relevância na Pesquisa
46.801924%
Symmetry has attracted a substantial amount of effort because considerable simplifications are possible in the mathematical and physical treatment of phenomena and natural systems that possess a certain degree of symmetry. Among physical and chemical systems the most widely known are those related to crystals and fluids. Whereas crystals have a lattice structure and a symmetry caused by ‘perfect’ order which can be classified by mathematical symmetry groups, most fluids have an average isotropic, highly-disordered ‘structure’ that is often considered to be random.Asymmetry is widely encountered in Biology and ecological systems- from amino acids to trees forests, and tribes, from physiological processes to anatomy- one often finds asymmetry to be present , although symmetries are also encountered whenever nature affords it. An important case is that of cell biomembranes that possess a marked structural and functional asymmetry which is essential to the survival of cells and microorganisms. Asymmetry both in time and selection ‘criteria’ plays a key role in the evolution of organisms and species.