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Reverse transcribing viruses replicate their genomes by reverse transcribing DNA copies from their RNA; these DNA copies are then transcribed to new RNA. Retrotransposons also spread by copying DNA and RNA from one another, [66] and telomerase contains an RNA that is used as template for building the ends of eukaryotic chromosomes. [67]
It is the first step of viral replication. Some viruses attach to the cell membrane of the host cell and inject its DNA or RNA into the host to initiate infection. Attachment to a host cell is often achieved by a virus attachment protein that extends from the protein shell (), of a virus.
Phylogeny of Orthornavirae RNA-dependent polymerase. The five colored branches are the five phyla of Orthornavirae.. Both kingdoms in Riboviria show a relation to the reverse transcriptases of group II introns that encode RTs and retrotransposons, which are self-replicating DNA sequences, the latter of which self-replicate via reverse transcription and integrate themselves into other parts of ...
A second version of the central dogma is popular but incorrect. This is the simplistic DNA → RNA → protein pathway published by James Watson in the first edition of The Molecular Biology of the Gene (1965). Watson's version differs from Crick's because Watson describes a two-step (DNA → RNA and RNA → protein) process as the central ...
This is the single largest group of RNA viruses [23] and has been organized by the ICTV into the phyla Kitrinoviricota, Lenarviricota, and Pisuviricota in the kingdom Orthornavirae and realm Riboviria. [24] Positive-strand RNA viruses can also be classified based on the RNA-dependent RNA polymerase. Three groups have been recognised: [25]
A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. [2] After invading a host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus retro (backward).
Some viruses (such as HIV, the cause of AIDS), have the ability to transcribe RNA into DNA. HIV has an RNA genome that is reverse transcribed into DNA. The resulting DNA can be merged with the DNA genome of the host cell. The main enzyme responsible for synthesis of DNA from an RNA template is called reverse transcriptase. [65]
For this reason, these viruses are called positive-sense RNA viruses. [35] In other RNA viruses, the RNA is a complementary copy of mRNA and these viruses rely on the cell's or their own enzyme to make mRNA. These are called negative-sense RNA viruses. In viruses made from DNA, the method of mRNA production is similar to that of the cell.