Circoviridae
Encyclopedia
The Circoviridae are a family of virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

es. These are small, relatively poorly-studied viruses, with circular, single-stranded DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 genomes of approximately one to four kilobases

Virology

The virons are non enveloped about 20 nanometers in diameter with icosahedral symmetry - triangulation number (T) = 1. The capsid consists of 12 pentagonal trumpet shaped pentomers.

The genome is monopartite, circular, single-stranded DNA of between 1.8 to 3.8 kilobases. There are two main open reading frames arranged in opposite directions that encode the replication (Rep) and capsid (Cap) proteins. Alternative start codons are common in the avian species.

The viruses replicate their genomes via a rolling circle mechanism. A stem loop structure with a conserved nonanucleotide motif is located at the 5' intergenic region of circovirus genomes and is thought to initiate rolling-cycle replication.

Taxonomy

The family Circoviridae contains three genera, Circovirus, Cyclovirus and Gyrovirus
Gyrovirus
The genus Gyrovirus, the only well known species being the chicken anemia virus, is a part of the family of Circoviridae, and consists of a nonenveloped, round, icosahedral capsid, 19-27 nm in diameter. The genome contained within consists of a single molecule of circular, single-stranded...

.

Two circoviruses have been identified in fish - Barbel circovirus (BaCV) 1 and 2. Their genomes are in length and contain two major open reading frames similar to the capsid and replication associated protein genes found in other circoviruses.
  • Genus Circovirus: type species: Porcine circovirus
    Porcine circovirus
    Porcine circovirus is a single-stranded DNA virus , that is nonenveloped with an unsegmented circular genome. The viral capsid is icosahedral and approximately 17 nm in diameter. PCV is a member of the virus family Circoviridae....

     type 1 and 2, beak and feather disease virus (BFDV)

  • Genus Cyclovirus : Dragonfly cyclovirus

  • Genus Gyrovirus
    Gyrovirus
    The genus Gyrovirus, the only well known species being the chicken anemia virus, is a part of the family of Circoviridae, and consists of a nonenveloped, round, icosahedral capsid, 19-27 nm in diameter. The genome contained within consists of a single molecule of circular, single-stranded...

    : type species: Chicken anaemia virus
    Chicken anaemia virus
    -Introduction:Chicken anaemia virus, or CAV, is a member of the circoviridae family. It is a non-enveloped icosahedral single stranded DNA virus....


External links

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