1,720,997 research outputs found
Molecular cytogenetic dissection of human chromosomes 3 and 21 evolution
No full textChromosome painting in placental mammalians illustrates that genome evolution is marked by chromosomal synteny conservation and that the association of chromosomes 3 and 21 may be the largest widely conserved syntenic block known for mammals. We studied intrachromosomal rearrangements of the syntenic block 3/21 by using probes derived from chromosomal subregions with a resolution of up to 10-15 Mbp. We demonstrate that the rearrangements visualized by chromosome painting, mostly translocations, are only a fraction of the actual chromosomal changes that have occurred during evolution. The ancestral segment order for both primates and carnivores is still found in some species in both orders. From the ancestral primate/carnivore condition an inversion is needed to derive the pig homolog, and a fission of chromosome 21 and a pericentric inversion is needed to derive the Bornean orangutan condition. Two overlapping inversions in the chromosome 3 homolog then would lead to the chromosome form found in humans and African apes. This reconstruction of the origin of human chromosome 3 contrasts with the generally accepted scenario derived from chromosome banding in which it was proposed that only one pericentric inversion was needed. From the ancestral form for Old World primates (now found in the Bornean orangutan) a pericentric inversion and centromere shift leads to the chromosome ancestral for all Old World monkeys. Intrachromosomal rearrangements, as shown here, make up a set of potentially plentiful and informative markers that can be used for phylogenetic reconstruction and a more refined comparative mapping of the genome
The Transcriptional Activity of Individual Ribosomal Dna Gene Clusters Is Modulated By Serum Concentration
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Comparative fluorescence in situ hybridization mapping of primate chromosomes with Alu polymerase chain reaction generated probes from human/rodent somatic cell hybrids
No full textWe have used Alu polymerase chain reaction generated probes from rearranged human/rodent somatic cell hybrids for fluorescence in situ hybridization and comparative mapping of some intrachromosomal changes in the karyotypes of great apes (Pan troglodytes, P. paniscus, Gorilla gorilla, Pongo pygmaeus), a gibbon (Hylobates lar), and an Old World monkey (Macaca fuscata). Probes containing chromosomes 2 and 18 fragments confirmed inversions already suggested by the banding pattern of great ape homologues. However, a chromosome 3 fragment showed complex rearrangements in the gibbon and macaque karyotype which were previously not well defined from banding. 'Subchromosomal painting' will allow the identification of intrachromosomal changes on the basis of DNA homology and provides a powerful method to study karyological and genomic evolution
Mapping through somatic cell hybrids and cDNA probes of protein C to chromosome 2, factor X to chromosome 13 and alfa-1-acid glycoprotein to chromosome 9
No full textAppropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Human genome dispersal and evolution of 4q35 duplications and interspersed LSau repeats
No full textWe have investigated the evolutionary history of the 4q35 paralogous region, and
of a sub-family of interspersed LSau repeats. In HSA, 4q35 duplications were
localized at 1q12, 3p12.3, 4q35, 10q26, 20cen, whereas duplicons and
interspersed LSau repeats simultaneously labeled the p arm of acrocentric
chromosomes. A multi-site localization of 4q35-like sequences was also observed
in PTR, GGO, PPY, HLA (Hominoidea) and PAN (Old World monkey), thus indicating
that duplications of this region have occurred extensively in the two clades,
which diverged at least 25 million years ago. In HSA, PTR and PAN, 4q35-derived
duplicons co-localized with rDNA, whereas in GGO and PPY this association was
partially lacking. In PAN, the single- and multi-site distribution of rDNA and
paralogous sequences, respectively, indicates a different timing of sequence
dispersal. The sub-family of interspersed LSau repeats showed a lesser dispersal
than 4q35 duplications both in man and great apes. This finding suggests that
duplications and repeated sequences have undergone different
expansion/contraction events during evolution. The mechanisms underlying the
dispersal of paralogous regions may be further derived through studies comparing
the detailed structural organization of these genomic regions in man and
primates
Mapping through somatic cell hybrids and cDNA probes of protein C to chromosome 2, factor X to chromosome 13 and alfa-1-acid glycoprotein to chromosome 9
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