Classification of Viral Genomes. Currently, over 4000 viruses have been described, classified into 71 families. Even though viruses possess small genomes, they exhibit enormous diversity compared with plants, animals and even bacteria.
Viral genomes are very diverse, since they can be DNA or RNA, single- or double-stranded, linear or circular, and vary in length and in the number of DNA or RNA molecules. The viral replication process begins when a virus infects its host by attaching to the host cell and penetrating the cell wall or membrane.
Thus, genomes approximately up to 25 kb in size are represented by both types of nucleic acids (DNA or RNA) and various topologies (circular, linear, segmented). All genomes larger than that are represented only by circular or linear dsDNA (Fig.
What is a virion vs virus?
A virion is an entire virus particle consisting of an outer protein shell called a capsid and an inner core of nucleic acid (either ribonucleic or deoxyribonucleic acid—RNA or DNA). The core confers infectivity, and the capsid provides specificity to the virus.
Although viruses are generally the smallest genomes, as a collection of biological genomes they exhibit the greatest variation. The major difference is that some of the genomes are DNA whereas others are RNA. In addition, both DNA and RNA genomes can be either double- or single-stranded (ds or ss).
What is monopartite genome?
Monopartite refers to the class of genome that is presented in the genome of the virus. As opposed to multipartite, viruses composed of monopartite genomes have a single molecule of nucleic acid. Most dsDNA viruses are monopartite.
Why do viruses have small genomes?
Small genome size is perfectly suited to virus replication, in which each infected host cell produces many copies of the viral genes from a single template. Such exponential replication places a premium on small genome size: the smaller the genome, the faster it can replicate.
Which viruses have segmented genomes?
Among viruses that infect vertebrates, those that carry segmented genomes belong to the Arenaviridae, Birnaviridae, Bunyavirales, Orthomyxoviridae, Picobirnaviridae, and Reoviridae. Reassortment has been documented to occur in nature for each of these viral taxa [1–6].
What do u mean by virion?
virion, an entire virus particle, consisting of an outer protein shell called a capsid and an inner core of nucleic acid (either ribonucleic or deoxyribonucleic acid—RNA or DNA). The core confers infectivity, and the capsid provides specificity to the virus.
Who proposed that virus and virion are different?
A virion is not the same as a virus. I define virus as a distinct biological entity with five different characteristics. Others believe that the virus is actually the infected host cell. The idea that virus and virion are distinct was first proposed by Bandea in 1983.
Who is father of virology?
Martinus Beijerinck is often called the Father of Virology.