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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.
This is a list of mnemonics used in medicine and medical science, categorized and alphabetized. A mnemonic is any technique that assists the human memory with information retention or retrieval by making abstract or impersonal information more accessible and meaningful, and therefore easier to remember; many of them are acronyms or initialisms which reduce a lengthy set of terms to a single ...
The virus then releases its genetic material (either single- or double-stranded RNA or DNA) into the cell. In some viruses this genetic material is circular and mimics a bacterial plasmid . At this stage the cell becomes infected and can also be targeted by the immune system.
Baltimore classification groups viruses together based on their manner of mRNA synthesis. Characteristics directly related to this include whether the genome is made of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA), the strandedness of the genome, which can be either single- or double-stranded, and the sense of a single-stranded genome, which is either positive or negative.
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 .
Many viruses replicate this way. The enzymes that copy RNA to new RNA, called RNA-dependent RNA polymerases, are also found in many eukaryotes where they are involved in RNA silencing. [11] RNA editing, in which an RNA sequence is altered by a complex of proteins and a "guide RNA", could also be seen as an RNA-to-RNA transfer.
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.
5' small nucleolar RNA capped and 3' polyadenylated long noncoding RNA - SRP RNA: signal recognition particle RNA CL00003: ssRNA single stranded RNA - stRNA: small temporal RNA - tasiRNA: trans-acting siRNA - tmRNA: transfer-messenger RNA RF00023: Bacterial RNA molecule with dual tRNA-like and messenger RNA-like properties uRNA U spliceosomal ...