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Viral eukaryogenesis is the hypothesis that the cell nucleus of eukaryotic life forms evolved from a large DNA virus in a form of endosymbiosis within a methanogenic archaeon or a bacterium. The virus later evolved into the eukaryotic nucleus by acquiring genes from the host genome and eventually usurping its role.
Viral evolution is a subfield of evolutionary biology and virology concerned with the evolution of viruses. [1] [2] Viruses have short generation times, and many—in particular RNA viruses—have relatively high mutation rates (on the order of one point mutation or more per genome per round of replication).
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. [1] Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. [2] [3] Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity.
A virus with this "viral envelope" uses it—along with specific receptors—to enter a new host cell. Viruses vary in shape from the simple helical and icosahedral to more complex structures. Viruses range in size from 20 to 300 nanometres; it would take 33,000 to 500,000 of them, side by side, to stretch to 1 centimetre (0.4 in).
Cell nucleus: A cell's information center, the cell nucleus is the most conspicuous organelle found in a eukaryotic cell. It houses the cell's chromosomes , and is the place where almost all DNA replication and RNA synthesis ( transcription ) occur.
The healthy virome consists of three distinct components: (i) viruses that systematically enter the human organism, primarily, with food, but do not replicate in humans; (ii) viruses infecting prokaryotes and, possibly, unicellular eukaryotes that comprise the healthy human microbiome; and (iii) viruses that actually replicate and persist in ...
Viruses using both DNA and RNA in their replication (retroviruses) range in size from 7,040 to 12,195 nucleotides. [15] The smallest double-stranded DNA viruses are the hepadnaviruses such as hepatitis B , at 3.2 kb and 42 nm (4.2 × 10 −5 mm); parvoviruses have smaller capsids, at 18–26 nm (1.8 × 10 −5 –2.6 × 10 −5 mm), but larger ...
Viruses in the first three kingdoms infect prokaryotes, and viruses in Shotokuvirae infect eukaryotes and include the atypical members of the realm. Viruses in Monodnaviria appear to have come into existence independently multiple times from circular bacterial and archaeal plasmids that encode the HUH endonuclease.