2 Genomes. Viral genomes consist of DNA or RNA only, never both. DNA and RNA molecules can be double stranded or single stranded, linear or circular (Fig. 1.6), segmented (composed of multiple pieces of nucleic acid) or nonsegmented.
Viral genomes are circular, as in the polyomaviruses, or linear, as in the adenoviruses. The type of nucleic acid is irrelevant to the shape of the genome. Among RNA viruses and certain DNA viruses, the genome is often divided up into separate parts, in which case it is called segmented.
RNA viral genomes are broadly divided into double stranded RNA, positive and negative strand single stranded RNAs, monopartite and multipartite RNA viruses.
The virus’s genome is uncoated from the protein and injected into the host cell. Then the viral genome hijacks the host cell’s machinery, forcing it to replicate the viral genome and produce viral proteins to make new capsids. Next, the viral particles are assembled into new viruses.
What is a virus composed of?
A virus is made up of a core of genetic material, either DNA or RNA, surrounded by a protective coat called a capsid which is made up of protein. Sometimes the capsid is surrounded by an additional spikey coat called the envelope.
How is a virus organized?
All viruses contain nucleic acid, either DNA or RNA (but not both), and a protein coat, which encases the nucleic acid. Some viruses are also enclosed by an envelope of fat and protein molecules. In its infective form, outside the cell, a virus particle is called a virion.
The envelopes are typically derived from portions of the host cell membranes (phospholipids and proteins), but include some viral glycoproteins. They may help viruses avoid the host immune system. Glycoproteins on the surface of the envelope serve to identify and bind to receptor sites on the host’s membrane.
What are the 4 steps in the correct order of virus infection?
Entry, the first step of virus infection, involves the recognition of viral receptor by a virus particle. The viral entry can be divided into four steps: attachment, penetration, cytoplasmic trafficking, and uncoating.
Which virus has DNA as its genome?
DNA viruses comprise important pathogens such as herpesviruses, smallpox viruses, adenoviruses, and papillomaviruses, among many others.
Which virus has DNA genome?
1.47. 2.1 Virus With DNA
|Virus family||Examples (common names)||Capsid symmetry|
|Hepadnaviridae||Hepatitis B virus||Icosahedral|
|Herpesviridae||Herpes simplex virus, varicella-zoster virus, cytomegalovirus, Epstein–Barr virus, varicella virus||Icosahedral|
|Papillomaviridae||Human papillomavirus, bovine papillomavirus||Icosahedral|
What are 5 characteristics of viruses?
These are: 1) attachment; 2) penetration; 3) uncoating; 4) replication; 5) assembly; 6)release. As shown in , the virus must first attach itself to the host cell.
What 2 components do all viruses contain?
The simplest virions consist of two basic components: nucleic acid (single- or double-stranded RNA or DNA) and a protein coat, the capsid, which functions as a shell to protect the viral genome from nucleases and which during infection attaches the virion to specific receptors exposed on the prospective host cell.
What are the 3 parts of a virus?
Viruses of all shapes and sizes consist of a nucleic acid core, an outer protein coating or capsid, and sometimes an outer envelope.
Does a virus contain DNA and RNA?
Virus. A virus is a small collection of genetic code, either DNA or RNA, surrounded by a protein coat. A virus cannot replicate alone. Viruses must infect cells and use components of the host cell to make copies of themselves.