1,721,152 research outputs found
Evolution of the dystrophin muscular promoter and 5 ' flanking region in primates
No full textAbout 1.6 kb of the noncoding region upstream of the muscular dystrophin gene was sequenced in human and other primates. The alignment showed the existence of many stretches of conserved sequences among the compared species distributed all along the investigated fragment, including the 5' end. In correspondence to these conserved boxes, we identified several new putative cis-acting elements that have similarity to known control regions of other muscle-specific genes. In some cases, however, the conserved sequences did not correspond to any known transcription factor binding sites. The rate of evolution estimated site by site all along the investigated region revealed a nonhomogeneous distribution of the substitution rate, several sequences exhibited a very slow rate of evolution suggesting that evolutionary forces of different nature may be at work. On the basis of the sequence alignment, we reconstructed the phylogenetic relationships within the hominoid lineage. In addition, we estimated the relative rate of evolution between hominoid and Old World monkeys, confirming the existence of an evolutionary slowdown in the hominoid lineage
Krill: a possible model for investigating the effects of ocean currents on the genetic structure of a pelagic invertebrate
No full textThis paper reviews the information available on the population genetics and systematics of krill (Euphausiidae, Crustacea), integrating the published data with new data collected in our laboratory. Phylogenetic analysis of several Antarctic and sub-Antarctic Euphausia species indicates the importance of dispersal in determining the present-day geographic distribution. Dating speciation events suggest that the formation of the Antarctic Convergence, the oceanographic barrier isolating the Southern Ocean, may have played a role in separating the ancestral Antarctic and sub-Antarctic lineages. Intraspecific data show that the Antarctic krill (Euphausia superba) is characterized by weak genetic differentiation, whereas the northern krill (Meganyctiphanes norvegica) is more structured showing discrete genetic pools. This difference can be explained, at least partly, by the oceanographic conditions in the areas inhabited by the two species
Effects of pollution on heterozygosity in the barnacle Balanus amphitrite Darwin (Cirripedia: Thoracica)
No full textThe effects of thermal and chemical pollution on gene and genotype frequencies and on multilocus structure were studied in 3 populations of the barnacle Balanus amphitrite Darwin from the lagoon of Venice, Italy. One of these populations (A) was subjected to high chemical pollution; the second (B) was constantly exposed to temperatures about 10-degrees-C higher than the rest of the lagoon since it was settled in front of an electric power plant outflow; and the third (C) was sampled in an unpolluted area of the lagoon as a control. Juvenile and adult age classes of each of the 3 samples were studied by electrophoretic analysis of the polymorphic loci Mpi, Pgi and Pgm. Significant differences were found between Population A adults and both B and C adults for the majority of the genetic comparisons. B and C adult populations did not differ significantly. Statistical comparisons among the 3 juvenile populations showed a high genetic homogeneity. Comparisons between the 2 age classes within each of the 3 populations exhibited significant differences only between adults and juveniles of Population A at the level of gene and genotype frequencies. Moreover, in Population A a significantly higher survival of the multi-homozygote class was observed. No differences were detected between adults and juveniles of B and C samples. These results suggest the action, in Population A, of some selective factor during the post-settlement period. Thermal pollution does not seem to play any important selective role. The hypothesis is advanced that selection is operated by heavy metals
Antarctic fish hemoglobins: evidence of adaptive evolution at subzero temperature
No full textNotothenioids represent a large group of marine teleosts that are mostly endemic to the Antarctic Ocean. In this environment, the low metabolic demand and the high oxygen concentration reduce the need for hemoglobin(s) [Hb(s)]. The extreme condition is represented by the icefish (Channichthyidae, Notothenioidei), the only vertebrates that lack Hb. We obtained the nucleotide sequence coding for the beta-globin chain of the single major Hb form in six red-blooded notothenioids. These included Gymnodraco acuticeps, one of the closest species to the Hb-less icefish, which is also the only known fish having a single Hb without Bohr effect. This species shows a higher rate of nonsynonymous substitutions (K-A), in contrast with the homogeneity of synonymous substitution (K-S) rates, and K-A/K-S ratios significantly greater than one in the majority of comparisons. These results are suggestive of positive selection, diversifying the single major Hb toward specialized functions. A single Hb that is free to diversify means that its role in routine oxygen transport can be reduced in the presence of a combination of physiological, ecological, and environmental factors. Although a reduced "routine" function for Hb, as is apparent in G. acuticeps, might, indeed, evoke the lack of Hb in icefish, evidence of diversifying selection reported here is at variance with the hypothesis of a simple trend from a single Hb toward the Hb-less condition
Inherited disease in dogs: molecular genetics applied to diagnosis
No full textThe recent progresses of molecular genetics and biotechnology allowed to significantly advance in the field of biomedical sciences. These extraordinary progresses also regarded species of veterinary interest such as dog, the genome of which was completely sequenced. More than 350 dog-breed gene pools combined to new powerful technologies represent a unique opportunity to investigate the molecular basis of inherited canine disorders as well as to develop appropriate test for quick and accurate molecular diagnosis
Strategies for microsatellite isolation: a review
No full textIn the last few years microsatellites have become one of the most popular molecular markers used with applications in many different fields. High polymorphism and the relative ease of scoring represent the two major features that make microsatellites of large interest for many genetic studies. The major drawback of microsatellites is that they need to be isolated de novo from species that are being examined for the first time. The aim of the present paper is to review the various methods of microsatellite isolation described in the literature with the purpose of providing useful guidelines in making appropriate choices among the large number of currently available options. In addition, we propose a fast and easy protocol which is a combination of different published methods
The mitochondrial genome of the ascalaphid owlfly <it>Libelloides macaronius </it>and comparative evolutionary mitochondriomics of neuropterid insects
Full text linkAbstract Background The insect order Neuroptera encompasses more than 5,700 described species. To date, only three neuropteran mitochondrial genomes have been fully and one partly sequenced. Current knowledge on neuropteran mitochondrial genomes is limited, and new data are strongly required. In the present work, the mitochondrial genome of the ascalaphid owlfly Libelloides macaronius is described and compared with the known neuropterid mitochondrial genomes: Megaloptera, Neuroptera and Raphidioptera. These analyses are further extended to other endopterygotan orders. Results The mitochondrial genome of L. macaronius is a circular molecule 15,890 bp long. It includes the entire set of 37 genes usually present in animal mitochondrial genomes. The gene order of this newly sequenced genome is unique among Neuroptera and differs from the ancestral type of insects in the translocation of trnC. The L. macaronius genome shows the lowest A+T content (74.50%) among known neuropterid genomes. Protein-coding genes possess the typical mitochondrial start codons, except for cox1, which has an unusual ACG. Comparisons among endopterygotan mitochondrial genomes showed that A+T content and AT/GC-skews exhibit a broad range of variation among 84 analyzed taxa. Comparative analyses showed that neuropterid mitochondrial protein-coding genes experienced complex evolutionary histories, involving features ranging from codon usage to rate of substitution, that make them potential markers for population genetics/phylogenetics studies at different taxonomic ranks. The 22 tRNAs show variable substitution patterns in Neuropterida, with higher sequence conservation in genes located on the α strand. Inferred secondary structures for neuropterid rrnS and rrnL genes largely agree with those known for other insects. For the first time, a model is provided for domain I of an insect rrnL. The control region in Neuropterida, as in other insects, is fast-evolving genomic region, characterized by AT-rich motifs. Conclusions The new genome shares many features with known neuropteran genomes but differs in its low A+T content. Comparative analysis of neuropterid mitochondrial genes showed that they experienced distinct evolutionary patterns. Both tRNA families and ribosomal RNAs show composite substitution pathways. The neuropterid mitochondrial genome is characterized by a complex evolutionary history.</p
Mitochondrial DNA sequence variation in the European sea bass, Dicentrarchus labrax L. (Serranidae): evidence of differential haplotype distribution in natural and farmed populations
No full textPCR and direct sequencing of 300 to 377-bp fragments of the cytochrome b mitochondrial gene were carried out in 40 specimens of European sea bass, Dicentrarchus labrax L., collected at different sites in the Mediterranean basin and representing wild and farmed populations. Sequence analysis revealed 6 transitional changes, which generated 5 different haplotypes (A-E). Only one mutation was nonsynonymous because it occurred in the first position of a codon leading to the replacement of valine by isoleucine. The genotypic distribution revealed that haplotype B was not present in the farm samples, whereas its frequency in the wild samples exceeded 30%. In contrast, haplotypes D and E were found in farmed populations but not in the wild populations. The comparison among wild populations showed a nonhomogeneous distribution of the two most frequent haplotypes, A and B
Messinian salinity crisis and the origin of freshwater lifestyle in Western Mediterranean gobies
No full textThe present paper reports on a molecular study based on 12S rRNA and 16S rRNA mitochondrial genes partly sequenced in 13 species of western Mediterranean gobies, three of which are strictly freshwater-dwelling. A total of 867 bp were aligned and used for the phylogenetic reconstruction. Two major lineages were identified, one clustering the sand gobies in a monophyletic clade. Relationships among taxa based on sequence analysis only partly match those based on morphological criteria, suggesting that the latter are somehow insufficient to correctly establish phylogenetic relationships within this family. The results provide evidence for a multiple independent evolution of the freshwater lifestyle in Knipowitschia and Padogobius lineages. On the basis of the present results, it is uncertain whether the freshwater preference within the genus Padogobius originated twice independently in P. nigricans and P. martensii or only once in their common ancestor. Estimation of the ages of the two major lineages of this group of fish with a molecular clock (in combination with the construction of a linearized tree) suggests that they are much older (at least 40 Myr) than previously thought. Thus, there should be no correlation between their diversification and the Miocene-Pliocene geological events, including the so-called Messinian salinity crisis, which occurred about 10 MYA and is believed to have played a role in their evolution. Alternatively, these gobies would have an evolutionary rate at least fourfold faster than those of other vertebrates
Isolation and characterization of microsatellites in the Adriatic sturgeon (Acipenser naccarii)
No full textWe isolated and characterized seven polymorphic microsatellite loci from a partial genomic library of the Adriatic sturgeon (Acipenser naccarii) enriched for GATA repeats. Variability was tested in 20 specimens of this endangered species. Our data support the tetraploid condition for A. naccarii and will be useful for the investigation of the remnant genetic variability of this species as well as for genetic tagging studies
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