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ONE FOOT IN, ONE FOOT OUT. “The outcome of the phylogenetic analysis of the universal genes of giant viruses is (at least, in principle) readily interpretable: the placement of the viral genes outside the three traditional domains of cellular life is compatible with the fourth-domain hypothesis, whereas their reliable placement inside any of the three domains would falsify this hypothesis.” https://lnkd.in/eU7uHHB View in LinkedIn

OVERLAP WITH RIBOSOMAL RNA DOMAINS. “Unlike other viruses, the giant viruses encode several proteins that are universal among cellular life forms, in particular translation system components, such as aminoacyl-tRNA synthetases and translation factors. The presence of these universal genes allows one to formally include the giant viruses in the “tree of life” that constitutes the basis of the three-domain system.” http://onlinelibrary.wiley.com/doi/10.1111/nyas.12728/full View in LinkedIn

RIBOSOMAL RNA DOMAINS. “In contrast, the specific fourth-domain hypothesis drives directly from the original definition of the three domains of cellular life. These three domains, Bacteria, Archaea, and Eukaryota, are the three major trunks in the unrooted phylogenetic tree of 16S ribosomal RNA, which is topologically consistent with the phylogenies of most of the other (nearly) universal genes that encode primarily components of the translation and the core transcription machineries.” http://onlinelibrary.wiley.com/doi/10.1111/nyas.12728/full View in LinkedIn

UNKNOWN GENE SOURCE. “In general terms, the claim that giant viruses represent a fourth domain of life simply refers to the cell-like character of these viruses in terms of size of the virions and genomes and, in addition, to the observation that many genes of these viruses have no detectable homologs and so could have come from some unknown source.” http://onlinelibrary.wiley.com/doi/10.1111/nyas.12728/full View in LinkedIn

EMPTY HANDED. “Jenner went to London in search of volunteers for vaccination. However, after 3 months he had found none.” https://lnkd.in/eQfnZZv View in LinkedIn

EVOLUTION OF VIRUSES. “The fourth-domain concept is sometimes presented as a general idea and on other occasions as a specific hypothesis on the evolution of viruses.” http://onlinelibrary.wiley.com/doi/10.1111/nyas.12728/full View in LinkedIn

EMPTY HANDED. “Jenner went to London in search of volunteers for vaccination. However, after 3 months he had found none.” https://lnkd.in/eQfnZZv View in LinkedIn

FOUTH DOMAIN. “The “cell-like” features of giant viruses prompted several researchers to propose the striking idea that giant viruses represent a “fourth domain of life” that is distinct from but comparable to the three cellular domains, bacteria, archaea, and eukaryotes.” https://lnkd.in/eU7uHHB View in LinkedIn

EMPTY HANDED. “Jenner went to London in search of volunteers for vaccination. However, after 3 months he had found none.” https://lnkd.in/eQfnZZv View in LinkedIn

TIP OF THE ICEBERG. “The recent identification of pandoraviruses and the pithovirus, which are not only huge, by viral standards, but also possess a novel, asymmetrical virion structure, shows that the actual diversity of giant viruses remains to be uncovered.” https://lnkd.in/eU7uHHB View in LinkedIn