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A virus has either a DNA or an RNA genome and is called a DNA virus or an RNA virus, respectively. Most viruses have RNA genomes. Plant viruses tend to have single-stranded RNA genomes and bacteriophages tend to have double-stranded DNA genomes. [26]: 96–99 Viral genomes are circular, as in the polyomaviruses, or linear, as in the ...
Life-cycle of a typical virus (left to right); following infection of a cell by a single virus, hundreds of offspring are released. When a virus infects a cell, the virus forces it to make thousands more viruses. It does this by making the cell copy the virus's DNA or RNA, making viral proteins, which all assemble to form new virus particles. [37]
The genomes of RNA viruses can be either single-stranded RNA or double-stranded RNA, and may contain one or more separate RNA molecules (segments: monopartit or multipartit genome). DNA viruses can have either single-stranded or double-stranded genomes. Most DNA virus genomes are composed of a single, linear molecule of DNA, but some are made ...
The coronavirus RNA genome has a 5′ methylated cap and a 3′ polyadenylated tail, which allows it to act like a messenger RNA and be directly translated by the host cell's ribosomes. The host ribosomes translate the initial overlapping open reading frames ORF1a and ORF1b of the virus genome into two large overlapping polyproteins, pp1a and ...
The initiator is the protein that recognizes the replicator and activates replication initiation. [ 1 ] Sometimes in bacteriology , the term "replicon" is only used to refer to chromosomes containing a single origin of replication and therefore excludes the genomes of archaea and eukaryotes which can have several origins.
The genetic material of a virus is stored within a viral protein structure called the capsid. The capsid is a "shield" that protects the viral nucleic acids from getting degraded by host enzymes or other types of pesticides or pestilences. It also functions to attach the virion to its host, and enable the virion to penetrate the host cell membrane.
In SARS-CoV-2, the spike protein, which has been imaged at the atomic level using cryogenic electron microscopy, [148] [149] is the protein responsible for allowing the virus to attach to and fuse with the membrane of a host cell; [147] specifically, its S1 subunit catalyzes attachment, the S2 subunit fusion.
Transcription produces a single-stranded RNA molecule known as messenger RNA, whose nucleotide sequence is complementary to the DNA from which it was transcribed. [51]: 6.1 The mRNA acts as an intermediate between the DNA gene and its final protein product. The gene's DNA is used as a template to generate a complementary mRNA.