Search results for "Phylogenetics"
showing 10 items of 777 documents
Phylogeny of viroids, viroidlike satellite RNAs, and the viroidlike domain of hepatitis delta virus RNA.
1991
We report a phylogenetic study of viroids, some plant satellite RNAs, and the viroidlike domain of human hepatitis delta virus RNA. Our results support a monophyletic origin of these RNAs and are consistent with the hypothesis that they may be "living fossils" of a precellular RNA world. Moreover, the viroidlike domain of human hepatitis delta virus RNA appears closely related to the viroidlike satellite RNAs of plants, with which it shares some structural and functional properties. On the basis of our phylogenetic analysis, we propose a taxonomic classification of these RNAs.
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 …
Molecular basis of adaptive convergence in experimental populations of RNA viruses
2002
Abstract Characterizing the molecular basis of adaptation is one of the most important goals in modern evolutionary genetics. Here, we report a full-genome sequence analysis of 21 independent populations of vesicular stomatitis ribovirus evolved on the same cell type but under different demographic regimes. Each demographic regime differed in the effective viral population size. Evolutionary convergences are widespread both at synonymous and nonsynonymous replacements as well as in an intergenic region. We also found evidence for epistasis among sites of the same and different loci. We explain convergences as the consequence of four factors: (1) environmental homogeneity that supposes an id…
Natural hybrids of S. cerevisiae×S. kudriavzevii share alleles with European wild populations of Saccharomyces kudriavzevii
2010
Saccharomyces kudriavzevii, a yeast species described from a pair of strains isolated from decayed leaves in Japan, has recently been isolated from oak barks in Portugal. Some data suggest that these European S. kudriavzevii populations could be closely related to the S. kudriavzevii genetic background present in natural hybrids isolated from wines and beers in different regions of Europe. However, a more exhaustive study of European S. kudriavzevii natural populations is necessary to confirm this observation. In this study, new S. kudriavzevii isolates were recovered from oak trees in different areas in Spain, and identified and characterized according to their molecular and physiological …
Molecules and Morphology, Phylogenetics and Genetics
1994
Various explanations can be offered for the incongruence between phylogenetic hypotheses resulting from morphological and molecular data sets. Of these, the possibility that incongruence may result from the mutation of major morphogenetic genes leading to dramatic morphological divergence unaccompanied by equivalent change of the phylogenetic marker molecule(s) used is discussed in detail. As evidence for this hypothesis, several examples for such incongruence are surveyed. It seems possible that in many cases the genetic basis of the morphological characters responsible for the incongruence found may be simple, and that the genes involved may be homologous to genes known from mutant system…
Molecular characterisation of the species of the genus Zygosaccharomyces.
2003
The restriction fragments polymorphisms of the mitochondrial DNA and the PCR fragment that comprised the internal transcribes spacers and the 5.8S rRNA gene, together with the electrophoretic karyotypes of 40 strains from the 10 species of the genus Zygosaccharomyces, including the new species Z. lentus were examined. The RFLP's of the ITS-5.8S region showed a specific restriction pattern for each species, including the new species Z. lentus. The only exception were the species Z. cidri and Z. fermentati that produced identical restriction profiles. The electrophoretic chromosome patterns confirmed the differences between the species of this genus, including the phylogenetic closest species…
Ty3/Gypsy Retrotransposons: Description of New Arabidopsis thaliana Elements and Evolutionary Perspectives Derived from Comparative Genomic Data
2000
We performed a comprehensive analysis of the evolution of the Ty3/GYPSY: group of long-terminal-repeat retrotransposons (also known as METAVIRIDAE:). Exhaustive database searches allowed us to detect novel elements of this group. In particular, the Arabidopsis thaliana and Drosophila melanogaster genome sequencing projects have recently disclosed a large number of new Ty3/GYPSY: sequences. So far, elements of three different Ty3/GYPSY: lineages had been described for A. thaliana. Here, we describe six new lineages, which we have called Tit-for-tat1, Tit-for-tat2, Gimli, Gloin, Legolas, and Little Athila. We confirm that plant Ty3/GYPSY: elements form two main monophyletic groups. Moreover, …
Cloning of Hsp70 genes from the marine sponges Sycon raphanus (Calcarea) and Rhabdocalyptus dawsoni (Hexactinellida). An approach to solve the phylog…
1997
The phylogenetic relationships among the three classes of the Porifera—Demospongiae, Calcarea and Hexactinellida—are still unresolved, despite the use of molecular analyses of rRNA. To determine whether phylogenetic resolution of these classes is possible based on genes coding for specific proteins, in the present study the genes for the 70 kDa heat shock protein [Hsp70] were isolated fromRhabdocalyptus dawsoni[Hexactinellida] and fromSycon raphanus[Calcarea], and compared to that previously isolated from the demospongeGeodia cydonium. The gene fromR. dawsoniis 2021 bp long and encodes a predicted Hsp70 of Mr77,697; the protein comprises the characteristic sites of eukaryotic, cytoplasmic H…
Bauplan of Urmetazoa: Basis for Genetic Complexity of Metazoa
2004
Sponges were first grouped to the animal-plants or plant-animals then to the Zoophyta or Mesozoa and finally to the Parazoa. Only after the application of molecular biological techniques was it possible to place the Porifera monophyletically with the other metazoan phyla, justifying a unification of all multicellular animals to only one kingdom, the Metazoa. The first strong support came from the discovery that cell-cell and cell-matrix adhesion molecules that were cloned from sponges and were subsequently expressed share a high DNA sequence and protein function similarity with the corresponding molecules of other metazoans. Besides these evolutionary novelties for Metazoa, sponges also hav…
Complete genome of a European hepatitis C virus subtype 1g isolate: phylogenetic and genetic analyses
2008
Abstract Background Hepatitis C virus isolates have been classified into six main genotypes and a variable number of subtypes within each genotype, mainly based on phylogenetic analysis. Analyses of the genetic relationship among genotypes and subtypes are more reliable when complete genome sequences (or at least the full coding region) are used; however, so far 31 of 80 confirmed or proposed subtypes have at least one complete genome available. Of these, 20 correspond to confirmed subtypes of epidemic interest. Results We present and analyse the first complete genome sequence of a HCV subtype 1g isolate. Phylogenetic and genetic distance analyses reveal that HCV-1g is the most divergent su…