Search results for "Biological evolution"

Genome size reduction through multiple events of gene disintegration in Buchnera APS

2001

The evolution of the endosymbiont Buchnera during its adaptation to intracellular life involved a massive reduction in its genome. By comparing the orthologous genes of Buchnera, Escherichia coli and Vibrio cholerae, we show that the minimal genome size of Buchnera arose from multiple events of gene disintegration dispersed over the whole genome. The elimination of the genes was a continuous process that began with gene inactivation and progressed until the DNA corresponding to the pseudogenes were completely deleted.

Subrepeats result from regional DNA sequence conservation in tandem repeats in Chironomus telomeres

1990

Repeat units, widespread in eukaryotic genomes, are often partially or entirely built up of subrepeats. Homogenization between whole repeat units arranged in tandem usually can best be understood as a result of unequal crossing over. Such a mechanism is less plausible for maintaining similarities between subrepeats within a repeat unit when present in a regular array. In Chironomus telomeres, large blocks of tandemly repeated approximately 350 base-pair units contain two or three pairs of subrepeats with high mutual identities, embedded in linker DNA, non-repetitive within the repeat unit. Measurements of evolutionary base changes in two closely related species, Chironomus tentans and Chiro…

Genetic analysis of heat shock response in three Drosophila species of the obscura group

1992

Heat shock response was investigated in three species of the obscura group of the Drosophila genus (D. subobscura, D. guanche, and D. madeirensis) by chromosome cytology analysis and [3H]uridine labeling. A set of eight puffs (2C, 15DE, 18C, 27A, 31CD, 85AB, 89A, and 94A) were induced after heat treatments in each of the three species; 18C, 27A, 89A, and 94A were the most heavily labeled in the autoradiograms after the induced conditions. From the in situ results using the major heat shock genes of D. melanogaster as a probe, it was inferred that the 18C, 94A, 89A, and 27A loci of the three obscura group species are homologous to D. melanogaster loci, which contain, HSP82, HSP70, HSP68, an…

Clonal Interference and the Evolution of RNA Viruses

1999

In asexual populations, beneficial mutations that occur in different lineages compete with one another. This phenomenon, known as clonal interference, ensures that those beneficial mutations that do achieve fixation are of large effect. Clonal interference also increases the time between fixations, thereby slowing the adaptation of asexual populations. The effects of clonal interference were measured in the asexual RNA virus vesicular stomatitis virus; rates and average effects of beneficial mutations were quantified.

The good-genes and compatible-genes benefits of mate choice.

2009

Genetic benefits from mate choice could be attained by choosing mates with high heritable quality ("good genes") and that are genetically compatible ("compatible genes"). We clarify the conceptual and empirical framework for estimating genetic benefits of mate choice, stressing that benefits must be measured from offspring fitness because there are no unequivocal surrogates for genetic quality of individuals or for compatibility of parents. We detail the relationship between genetic benefits and additive and nonadditive genetic variance in fitness, showing that the benefits have been overestimated in previous verbal treatments. We point out that additive benefits readily arise from nonaddit…

The evolution of RNA viruses: A population genetics view.

2000

RNA viruses are excellent experimental models for studying evolution under the theoretical framework of population genetics. For a proper justification of this thesis we have introduced some properties of RNA viruses that are relevant for studying evolution. On the other hand, population genetics is a reductionistic theory of evolution. It does not consider or make simplistic assumptions on the transformation laws within and between genotypic and phenotypic spaces. However, such laws are minimized in the case of RNA viruses because the phenotypic space maps onto the genotypic space in a much more linear way than on higher DNA-based organisms. Under experimental conditions, we have tested th…

Prisoner's dilemma in an RNA virus

1999

The evolution of competitive interactions among viruses1 was studied in the RNA phage φ6 at high and low multiplicities of infection (that is, at high and low ratios of infecting phage to host cells). At high multiplicities, many phage infect and reproduce in the same host cell, whereas at low multiplicities the viruses reproduce mainly as clones. An unexpected result of this study1 was that phage grown at high rates of co-infection increased in fitness initially, but then evolved lowered fitness. Here we show that the fitness of the high-multiplicity phage relative to their ancestors generates a pay-off matrix conforming to the prisoner's dilemma strategy of game theory2,3. In this strateg…

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…

Sequence Variability and Sequence Evolution: An Explanation of Molecular Polymorphisms and Why Many Molecular Structures Can Be Preserved Although Th…

2010

The existence of many processes that regulate RNA expression poses a challenge to the idea that the cell is the culmination of a highly efficient interplay of individual proteins, each with specific, highly specialized functions. It will be demonstrated here the extent to which the cell may undergo evolutionary processes that also occur in the macrocosmos, specifically with reference to the rules of mutation and preservation. These molecular evolutionary processes could facilitate a better understanding of the development of molecular structures and the functioning of the cell and could give an explanation of the molecular polymorphisms and also explain why many molecular structures can be …

Does the VP1 gene of foot-and-mouth disease virus behave as a molecular clock?

1992

We have carried out a phylogenetic study of the evolution of the VP1 gene sequence from different serological types and subtypes of foot-and-mouth disease virus (FMDV). The maximum-likelihood method developed by Hasegawa and co-workers (Hasegawa et al. 1985) for the estimation of evolutionary parameters and branching dates has been used to decide between alternative models of evolution: constant versus variable rates. The results obtained indicate that a constant rate model, i.e., a molecular clock, seems to be the most plausible one. However, additional information suggests the possibility that the appearance of serotype CS has been accompanied by an episode of rapid evolution (Villaverde …