1,721,023 research outputs found
Vitellogenin gene family in vertebrates: evolution and functions
No full textAbstract
The vitellogenin gene family is constituted of variable gene numbers encoding for polypeptides that are precursors of yolk
proteins and derivatives in oviparous and ovoviviparous vertebrates. The comprehension of which mechanisms have shaped
the evolution of vtg gene family represents an attractive field of research. The primary intent of this review is to summarize the
evolutionary hypotheses that have been proposed over recent decades, highlighting the differences between the proposed
models. Overall in vertebrates the evolutionary history of this gene family is the result of complex modifications deeply
influenced by events such as Whole Genome Duplications (WGDs), lineage-specific gene losses and duplications. Interestingly
the last hypothesis allowed to date the vitellogenin gene cluster origin in the common ancestor of gnathostomes. In addition, in
the last decades, several works evidenced non-nutritional functions such as antibacterial, immunological and antioxidant
activities overcoming its classical view as a simple source of nourishment for the developing embryos
Characterization of a Tc1-like transposon in the Antarctic ice-fish, Chionodraco hamatus.
No full textWe report the presence of Tc1 transposon-like sequences in the Antarctic ice-fish Chionodraco hamatus, belonging to the Notothenioidei. The complete DNA sequence of these transposon-like elements is reduced in length compared to other Tc1 transposons, but it appears to share significant structural similarities with them. It contains a degenerate open reading frame, whose inferred 264 amino acid sequence shares sequence similarity with the 'aspartic acid, aspartic acid (35) glutamic acid' family of transposases, particularly those from Caenorhabditis species (sp.) and Drosophila sp. Southern blot analysis and polymerase chain reaction amplification indicate that Tc1 transposonlike sequences are present in other notothenioid species, though their amount can vary in the different lineages. (C) 2002 Elsevier Science B.V. All rights reserved
Phylogenetic analysis of Veneridae (Bivalvia):comparison of molecular and palaeontological data
No full text
Molecular data from the 16S rRNA gene for the phylogeny of Veneridae (Mollusca: Bivalvia)
No full textMolecular data from 16S rRNA gene for the phylogeny of Veneridae (Mollusca: Bivalvia)
No full textVeneridae, a cosmopolitan and ubiquitous
family in world-wide littoral environments, lists more
than 500 species, many of which are often subject to
intensive commercial exploitation due to their numerical
dominance in benthic communities. Historically,
the family has been divided into 12 subfamilies by
M. Keen and, even though this taxonomical arrangement
was adopted for convenience and does not necessarily
reflect genetic relationships, as suggested by
Keen herself, this classification is still accepted. To
contribute to clarify the systematics and phylogeny of
Veneridae, the portion of the nucleotide sequence
corresponding to domains IV and V of the gene encoding
the large subunit of mitochondrial ribosomal
RNA was analysed in 14 species representative of 10
genera belonging to 6 different subfamilies. The results
obtained using the maximum-parsimony and neighbour-
joining methods indicate that the current placement
of the genera into subfamilies does not always
reflect a natural subdivision. In addition, the six species
of Tapetinae studied, though confirmed to be a monophyletic
clade, do not exhibit a correct attribution at
the genus level
The Ovulidae or egg-cowries: one of the most remarkable examples of camouflage among marine invertebrates
No full textORGANIZZAZIONE, COMPOSIZIONE DEL GENOMA ED EVOLUTIONARY RATE NELLE DIVERSE LINEE EVOLUTIVE DEI RETTILI
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