Ancient large-scale genome duplications: phylogenetic and linkage analyses shed light on chordate genome evolution |
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Authors: | Pebusque MJ; Coulier F; Birnbaum D; Pontarotti P |
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Institution: | Institut de Cancerologie et d'Immunologie de Marseille, INSERM U 119, France. |
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Abstract: | Paralogous genes from several families were found in four human chromosome
regions (4p16, 5q33-35, 8p12-21, and 10q24-26), suggesting that their
common ancestral region underwent several rounds of large- scale
duplication. Searches in the EMBL databases, followed by phylogenetic
analyses, showed that cognates (orthologs) of human duplicated genes can be
found in other vertebrates, including bony fishes. In contrast, within each
family, only one gene showing the same high degree of similarity with all
the duplicated mammalian genes was found in nonvertebrates (echinoderms,
insects, nematodes). This indicates that large-scale duplications occurred
after the echinoderms/chordates split and before the bony vertebrate
radiation. It has been suggested that two rounds of gene duplication
occurred in the vertebrate lineage after the separation of Amphioxus and
craniate (vertebrates + Myxini) ancestors. Before these duplications, the
genes that have led to the families of paralogous genes in vertebrates must
have been physically linked in the craniate ancestor. Linkage of some of
these genes can be found in the Drosophila melanogaster and Caenorhabditis
elegans genomes, suggesting that they were linked in the triploblast
Metazoa ancestor.
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