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Viral Quasispecies
A viral quasispecies is a population structure of viruses with a large number of variant genomes (related by mutations). Quasispecies result from high mutation rates as mutants arise continually and change in relative frequency as viral replication and selection proceeds. The theory predicts that a viral quasispecies at a low but evolutionarily neutral and highly connected (that is, flat) region in the fitness landscape will outcompete a quasispecies located at a higher but narrower fitness peak in which the surrounding mutants are unfit. This phenomenon has been called 'the quasispecies effect' or, more recently, the 'survival of the flattest'. The term quasispecies was adopted from a theory of the origin of life in which primitive replicons consisted of mutant distributions, as found experimentally with present-day RNA viruses within their host. The theory provided a new definition of wild type when describing viruses, and a conceptual framework for a deeper understanding of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Population Genetics
Population genetics is a subfield of genetics that deals with genetic differences within and between populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as adaptation, speciation, and population structure. Population genetics was a vital ingredient in the emergence of the modern evolutionary synthesis. Its primary founders were Sewall Wright, J. B. S. Haldane and Ronald Fisher, who also laid the foundations for the related discipline of quantitative genetics. Traditionally a highly mathematical discipline, modern population genetics encompasses theoretical, laboratory, and field work. Population genetic models are used both for statistical inference from DNA sequence data and for proof/disproof of concept. What sets population genetics apart from newer, more phenotypic approaches to modelling evolution, such as evolutionary game theory and adaptive dynamics, is its emphasis on such genetic phenomena as dominance, epi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA Viruses
''Orthornavirae'' is a kingdom of viruses that have genomes made of ribonucleic acid (RNA), those genomes encoding an RNA-dependent RNA polymerase (RdRp). The RdRp is used to transcribe the viral RNA genome into messenger RNA (mRNA) and to replicate the genome. Viruses in this kingdom also share a number of characteristics involving evolution, including high rates of genetic mutations, recombinations, and reassortments. Viruses in ''Orthornavirae'' belong to the realm ''Riboviria''. They are descended from a common ancestor that may have been a non-viral molecule that encoded a reverse transcriptase instead of an RdRp for replication. The kingdom is subdivided into five phyla that separate member viruses based on their genome type, host range, and genetic similarity. Viruses with three genome types are included: positive-strand RNA viruses, negative-strand RNA viruses, and double-stranded RNA viruses. Many of the most widely known viral diseases are caused by RNA viruses in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypercycle (chemistry)
In chemistry, a hypercycle is an abstract model of organization of self-replicating molecules connected in a cyclic, autocatalytic manner. It was introduced in an ordinary differential equation (ODE) form by the Nobel Prize in Chemistry winner Manfred Eigen in 1971 and subsequently further extended in collaboration with Peter Schuster. It was proposed as a solution to the error threshold problem encountered during modelling of replicative molecules that hypothetically existed on the primordial Earth (see: abiogenesis). As such, it explained how life on Earth could have begun using only relatively short genetic sequences, which in theory were too short to store all essential information. The hypercycle is a special case of the replicator equation. The most important properties of hypercycles are autocatalytic growth competition between cycles, once-for-ever selective behaviour, utilization of small selective advantage, rapid evolvability, increased information capacity, and selec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peter Schuster
Peter K. Schuster (born 7 March 1941) is a theoretical chemist known for his work with the German Nobel Laureate Manfred Eigen in developing the quasispecies model. His work has made great strides in the understanding of viruses and their replication, as well as theoretical mechanisms in the origin of life. Biography Schuster was born in Vienna, Austria and graduated with highest honors from "gymnasium". He studied chemistry and physics at the University of Vienna and earned his PhD in 1967. He was a Postdoc at the Max Planck Institute for Biophysical Chemistry. Together with Eigen, Schuster developed the quasispecies model. He is full professor of theoretical chemistry at the University of Vienna, the founding director of the Institute of Molecular Biotechnology in Jena, Germany, as well as the current head of its Department of Molecular Evolutionary Biology. He is an external faculty member at the Santa Fe Institute. Currently, Prof. Schuster is the President of the Austrian A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manfred Eigen
Manfred Eigen (; 9 May 1927 – 6 February 2019) was a German Biophysical chemistry, biophysical chemist who won the 1967 Nobel Prize in Chemistry for work on measuring fast chemical reactions. Eigen's research helped solve major problems in physical chemistry and aided in the understanding of chemical processes that occur in living organisms. In later years, he explored the biochemical roots of life and evolution. He worked to install a multidisciplinary program at the Max Planck Institute to study the underpinnings of life at the molecular level. His work was hailed for creating a new scientific and technological discipline: evolutionary biotechnology. Education and early life Eigen was born on 9 May 1927 in Bochum, the son of Hedwig (Feld) and Ernst Eigen, a chamber musician. As a child he developed a deep passion for music, and studied piano. World War II interrupted his formal education. At age fifteen he was drafted into service in a German antiaircraft unit. He was ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viral Quasispecies Figure 1
Viral means "relating to viruses" (small infectious agents). Viral may also refer to: Viral behavior, or virality Memetic behavior likened that of a virus, for example: * Viral marketing, the use of existing social networks to spread a marketing message * Viral phenomenon, relating to contagion theory or the "virality" of network culture, such as a meme * Viral video, a video that quickly attains a high popularity Titled works * ''Viral'' (2016 American film), a 2016 American science fiction horror drama * ''Viral'' (2016 Hindi film), an Indian Bollywood film based on social media * ''Viral'' (web series), a 2014 Brazilian comedy web series * '' V/H/S: Viral'', an American anthology horror film * '' Viral: The Search for the Origin of COVID-19'', a book by Alina Chand and Matt Ridley See also * ''Virals'', a novel series by Kathy Reichs * Virulence Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most, especially in animal system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adaptation
In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the population during that process. Thirdly, it is a phenotypic trait or adaptive trait, with a functional role in each individual organism, that is maintained and has evolved through natural selection. Historically, adaptation has been described from the time of the ancient Greek philosophers such as Empedocles and Aristotle. In 18th and 19th century natural theology, adaptation was taken as evidence for the existence of a deity. Charles Darwin proposed instead that it was explained by natural selection. Adaptation is related to biological fitness, which governs the rate of evolution as measured by change in allele frequencies. Often, two or more species co-adapt and co-evolve as they develop adaptations that interlock with those of the oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deep Sequencing
Coverage (or depth) in DNA sequencing is the number of unique reads that include a given nucleotide in the reconstructed sequence. Deep sequencing refers to the general concept of aiming for high number of unique reads of each region of a sequence. Rationale Even though the sequencing accuracy for each individual nucleotide is very high, the very large number of nucleotides in the genome means that if an individual genome is only sequenced once, there will be a significant number of sequencing errors. Furthermore, many positions in a genome contain rare single-nucleotide polymorphisms (SNPs). Hence to distinguish between sequencing errors and true SNPs, it is necessary to increase the sequencing accuracy even further by sequencing individual genomes a large number of times. Ultra-deep sequencing The term "ultra-deep" can sometimes also refer to higher coverage (>100-fold), which allows for detection of sequence variants in mixed populations. In the extreme, error-corrected sequ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lethal Mutagenesis
Error catastrophe refers to the cumulative loss of genetic information in a lineage of organisms due to high mutation rates. The mutation rate above which error catastrophe occurs is called the error threshold. Both terms were coined by Manfred Eigen in his mathematical evolutionary theory of the quasispecies. The term is most widely used to refer to mutation accumulation to the point of inviability of the organism or virus, where it cannot produce enough viable offspring to maintain a population. This use of Eigen's term was adopted by Lawrence Loeb and colleagues to describe the strategy of lethal mutagenesis to cure HIV by using mutagenic ribonucleoside analogs. There was an earlier use of the term introduced in 1963 by Leslie Orgel in a theory for cellular aging, in which errors in the translation of proteins involved in protein translation would amplify the errors until the cell was inviable. This theory has not received empirical support. Error catastrophe is predicte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extinction Vortex
Extinction vortices are a class of models through which conservation biologists, geneticists and ecologists can understand the dynamics of and categorize extinctions in the context of their causes. This model shows the events that ultimately lead small populations to become increasingly vulnerable as they spiral toward extinction. Developed by M. E. Gilpin and M. E. Soulé in 1986, there are currently four classes of extinction vortices. The first two (R and D) deal with environmental factors that have an effect on the ecosystem or community level, such as disturbance, pollution, habitat loss etc. Whereas the second two (F and A) deal with genetic factors such as inbreeding depression and outbreeding depression, genetic drift etc. Types of vortices *R Vortex: The R vortex is initiated when there is a disturbance which facilitates a lowering of population size (N) and a corresponding increase in variability (Var(r)). This event can make populations vulnerable to additional distu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Error Threshold (evolution)
In evolutionary biology and population genetics, the error threshold (or critical mutation rate) is a limit on the number of base pairs a self-replicating molecule may have before mutation will destroy the information in subsequent generations of the molecule. The error threshold is crucial to understanding "Eigen's paradox". The error threshold is a concept in the origins of life (abiogenesis), in particular of very early life, before the advent of DNA. It is postulated that the first self-replicating molecules might have been small ribozyme-like RNA molecules. These molecules consist of strings of base pairs or "digits", and their order is a code that directs how the molecule interacts with its environment. All replication is subject to mutation error. During the replication process, each digit has a certain probability of being replaced by some other digit, which changes the way the molecule interacts with its environment, and may increase or decrease its fitness, or ability ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unit Of Selection
A unit of selection is a biological entity within the hierarchy of biological organization (for example, an entity such as: a self-replicating molecule, a gene, a cell, an organism, a group, or a species) that is subject to natural selection. There is debate among evolutionary biologists about the extent to which evolution has been shaped by selective pressures acting at these different levels. There is debate over the relative importance of the units themselves. For instance, is it group or individual selection that has driven the evolution of altruism? Where altruism reduces the fitness of ''individuals'', individual-centered explanations for the evolution of altruism become complex and rely on the use of game theory, for instance; see kin selection and group selection. There also is debate over the definition of the units themselves, and the roles for selection and replication, and whether these roles may change in the course of evolution. Fundamental theory Two useful i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
