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M Stenico

Publications and source records attributed to M Stenico.

7 recordsLinked to original sources
PubMed1998

Mitochondrial lineages in Ladin-speaking communities of the eastern Alps.

European mitochondrial alleles cluster into five haplogroups. Haplogroup 2 is rare in general, but represents more than half of the few known sequences among Ladin speakers of the Alps. Here we describe DNA diversity in control region I of the hypervariable D-loop in 43 Ladins, and in 25 Italian speakers. Analysis of these data, and of previously published sequences, confirms a high degree of differentiation among Ladins and their geographical neighbours. This cannot be regarded as a simple effect of isolating factors, geographic or linguistic, as diversity is high within Ladin communities too. Rather, allele genealogies, population trees, and principal component analysis suggest a relationship between Ladin and Near Eastern samples. Two evolutionary hypotheses seem compatible with these findings. The view whereby Ladins could be descended from Palaeolithic inhabitants of the Alps is supported by the identification, in this study, of the probable ancestral haplotype of group 2, never previously observed in central Europe. Alternatively, a comparatively recent, Neolithic immigration of the ancestors of current Ladin speakers seems consistent with recent linguistic theories. In both cases, the number of lineages present, and their extensive diversity, are not compatible with a serious bottleneck in the Ladin population's history.

Alleles↗
PubMed1996

Mitochondrial DNA sequence variation across linguistic and geographic boundaries in Italy.

A previous investigation demonstrated the existence of extensive allele frequency diversity within an area of northern Italy crossed by a linguistic (dialect) boundary and by the Po River, either of them or both presumably constraining gene flow. We obtained hair samples from 45 school pupils from 9 localities in that area and sequenced a 255-bp segment of the mtDNA D loop. Estimates of the minimum number of migration events from gene genealogies suggest that the linguistic barrier impaired gene flow more than the river did. However, an analysis of molecular variance (AMOVA) showed that most sequence diversity occurs within rather than between populations and that the differences between groups of populations, defined either by linguistic or geographic criteria, do not reach significance. Three areas of rapid genetic variation were identified; their locations suggest that populations of the western part of the study area evolved in relative isolation. Therefore mtDNA sequence variation does not seem to reflect the same processes--drift and presence of dispersal barriers--that led to the observed distributions of nuclear allele frequencies.

Adolescent↗
PubMed1996

High mitochondrial sequence diversity in linguistic isolates of the Alps.

Segment I of the control region of mtDNA (360 bases) was sequenced in seven samples, each of 10 individuals inhabiting villages in the eastern Italian Alps (South Tyrol and Trentino). Three linguistic groups, German, Italian, and Ladin, were represented by two samples each; the seventh sample comes from an isolated group of German origin, the Mocheni, who are linguistically distinct and geographically separated from the bulk of the German speakers. Seventy-four polymorphic sites were identified, defining 63 different haplotypes. Mocheni and Ladin speakers tend to form two clusters in the evolutionary trees inferred from sequences. Analysis of molecular variance shows significant differentiation within samples, among them, and among linguistic groups. Genetic differences between the Ladins and the other groups are not much smaller than between Europeans and some Africans; variation is large within groups, as well, with the exception of only the Mocheni. In the evolutionary trees where the four alpine groups are compared with other European populations, Mocheni and especially Ladins appear as clear outliers. Romansch-speaking Swiss, who are linguistically related to Ladins, are not genetically similar to them, for this segment of DNA. Because the time elapsed since colonization of the Alps (< or = 12,000 years) is short in mutational terms, the only model accounting for the observed relationships between mtDNA variation and linguistic identity seems one in which a population ancestral to Ladin speakers was already differentiated long before the Alps were settled and the current linguistic affiliations were established. For the Mocheni, the results are consistent with a simpler episode of allele loss, from an original genetic pool common to the ancestors of the current German speakers.

DNA, Mitochondrial↗
PubMed1994

Codon usage in Caenorhabditis elegans: delineation of translational selection and mutational biases.

Synonymous codon usage varies considerably among Caenorhabditis elegans genes. Multivariate statistical analyses reveal a single major trend among genes. At one end of the trend lie genes with relatively unbiased codon usage. These genes appear to be lowly expressed, and their patterns of codon usage are consistent with mutational biases influenced by the neighbouring nucleotide. At the other extreme lie genes with extremely biased codon usage. These genes appear to be highly expressed, and their codon usage seems to have been shaped by selection favouring a limited number of translationally optimal codons. Thus, the frequency of these optimal codons in a gene appears to be correlated with the level of gene expression, and may be a useful indicator in the case of genes (or open reading frames) whose expression levels (or even function) are unknown. A second, relatively minor trend among genes is correlated with the frequency of G at synonymously variable sites. It is not yet clear whether this trend reflects variation in base composition (or mutational biases) among regions of the C.elegans genome, or some other factor. Sequence divergence between C.elegans and C.briggsae has also been studied.

Animals↗