Search results for "MUTATION"

2005

In this report we re-examine some recent experiments with digital organisms to test some predictions of quasispecies theory. These experiments revealed that under high mutation rates populations of less fit organisms previously adapted to such high mutation rates were able to outcompete organisms with higher average fitness but adapted to low mutation rates. We have verified that these results do hold in the original conditions and, by extending the set of initial parameters, we have also detected that the critical mutation rate was independent of population size, a result that we have found to be dependent on a different, contingent factor, the initial fitness vector. Furthermore, in all b…

Experimental Evolution and Population Genetics of RNA Viruses

2009

Viral studies have contributed substantially to the field of experimental evolution during the last two decades. The rapid evolution of RNA viruses makes them especially suitable for investigating real-time evolution, while their small genomes facilitate the analysis of the genetic basis of evolutionary change. We review recent advances in RNA virus experimental evolution, focusing on genetic properties that differentiate them from DNA-based organisms, such as their high mutation rates, small genome sizes, low genetic robustness, and the predominance of antagonistic epistasis. We argue that these properties can explain many aspects of RNA virus evolution, including rapid evolution, marked f…

Rate of deleterious mutation and the distribution of its effects on fitness in vesicular stomatitis virus

1999

Despite their importance, the parameters describing the spontaneous deleterious mutation process have not been well described in many organisms. If mutations are important for the evolution of every living organism, their importance becomes critical in the case of RNA-based viruses, in which the frequency of mutation is orders of magnitude larger than in DNA-based organisms. The present work reports minimum estimates of the deleterious mutation rate, as well as the characterization of the distribution of deleterious mutational effects on the total fitness of the vesicular stomatitis virus (VSV). The estimates are based on mutation-accumulation experiments in which selection against deleteri…

Multiple infection dynamics has pronounced effects on the fitness of RNA viruses

2001

Several factors play a role during the replication and transmission of RNA viruses. First, as a consequence of their enormous mutation rate, complex mixtures of genomes are generated immediately after infection of a new host. Secondly, differences in growth and competition rates drive the selection of certain genetic variants within an infected host. Thirdly, but not less important, a random sampling occurs at the moment of viral infectious passage from an infected to a healthy host. In addition, the availability of hosts also influences the fate of a given viral genotype. When new hosts are scarce, different viral genotypes might infect the same host, adding an extra complexity to the comp…

RNA viruses: a bridge between life and artificial life

1995

RNA viruses can be an adequate bridge between life and artificial life. Under experimental conditions the parameters that in last instance are responsible for the evolution of replicons resembling primitive life forms can be easily studied. One year of a RNA virus evolving may be equivalent to one million years of an evolving DNA-based entity. High mutation rates as well as very short life cycles permit the capability of observing evolutionary effects in the lifetime of a human observer. Another important feature of RNA viruses, functionally related to its mutation rate, is the genome length, which ranges between 3 and 30 Kb, probably the shortest lengths with the highest estimated mutation…

Intraclonal variation in RNA viruses: generation, maintenance and consequences

2003

This paper explores the evolutionary implications of the enormous variability that characterizes populations of RNA viruses and retroviruses. It begins by examining the magnitude of genetic variation in both natural and experimental populations. In natural populations, differences arise even within individual infected patients, with the per-site nucleotide diversity at this level ranging from <1% to 6%. In laboratory populations, two viruses sampled from the same clone differed by ∼0.7% in their fitness. Three different mechanisms that may be important in maintaining viral genetic variability were tested: (1) Fisher's fundamental theorem, to compare the observed rate of fitness change with …

The cost of replication fidelity in an RNA virus

2005

It is often argued that high mutation rates are advantageous for RNA viruses, because they confer elevated rates of adaptation. However, there is no direct evidence showing a positive correlation between mutation and adaptation rates among RNA viruses. Moreover, theoretical work does not argue in favor of this prediction. We used a series of vesicular stomatitis virus clones harboring single amino acid substitutions in the RNA polymerase to demonstrate that changes inducing enhanced fidelity paid a fitness cost, but that there was no positive correlation between mutation an adaptation rates. We demonstrate that the observed mutation rate in vesicular stomatitis virus can be explained by a t…

Spontaneous rate of clonal mutations inDaphnia galeata

2020

AbstractMutations are the ultimate source of heritable variation and therefore the fuel for evolution, but direct estimates exist only for few species. We estimated the spontaneous nucleotide mutation rate among clonal generations in the waterfleaDaphnia galeatawith a short term mutation accumulation approach. Individuals from eighteen mutation accumulation lines over five generations were deep genome sequenced to count de novo mutations that were not present in a pool of F1 individuals, representing the parental genotype. We identified 12 new nucleotide mutations in 90 clonal generational passages. This resulted in an estimated haploid mutation rate of 0.745 x 10-9(95% c.f. 0.39 x 10-9− 1.…

EXPERIMENTAL EVOLUTION OF RNA VERSUS DNA VIRUSES

2011

Based on their extremely high mutation rates, RNA viruses have been traditionally considered as the fastest evolving entities in nature. However, recent work has revealed that, despite their greater replication fidelity, single-stranded (ss) DNA viruses can evolve fast in a similar way. To further investigate this issue, we have compared the rates of adaptation and molecular evolution of ssRNA and ssDNA viruses under highly controlled laboratory conditions using the bacteriophages ΦX174, G4, f1, Qβ, SP, and MS2 as model systems. Our results indicate that ssRNA phages evolve faster than ssDNA phages under strong selective pressure, and that their extremely high mutation rates appear to be op…

Systematic screening for mutations in the human serotonin 1F receptor gene in patients with bipolar affective disorder and schizophrenia

1996

Using single strand conformational analysis we screened the complete coding sequence of the serotonin 1F (5-HT{sub 1F}) receptor gene for the presence of DNA sequence variation in a sample of 137 unrelated individuals including 45 schizophrenic patients, 46 bipolar patients, as well as 46 healthy controls. We detected only three rare sequence variants which are characterized by single base pair substitutions, namely a silent T{r_arrow}A transversion in the third position of codon 261 (encoding isoleucine), a silent C{r_arrow}T transition in the third position of codon 176 (encoding histidine), and a C{r_arrow}T transition in position -78 upstream from the start codon. The lack of significan…