Molecular virology

Molecular virology is the study of viruses on a molecular level. Viruses are submicroscopic parasites that replicate inside host cells. They are able to successfully infect and parasitize all kinds of life forms- from microorganisms to plants and animals- and as a result viruses have more biological diversity than the rest of the bacterial, plant, and animal kingdoms combined. Studying this diversity is the key to a better understanding of how viruses interact with their hosts, replicate inside them, and cause diseases. Molecular virology is the study of viruses on a molecular level. Viruses are submicroscopic parasites that replicate inside host cells. They are able to successfully infect and parasitize all kinds of life forms- from microorganisms to plants and animals- and as a result viruses have more biological diversity than the rest of the bacterial, plant, and animal kingdoms combined. Studying this diversity is the key to a better understanding of how viruses interact with their hosts, replicate inside them, and cause diseases. Viruses rely on their host to replicate and multiply. This is because viruses are unable to go through cell division, as they are acellular–meaning they lack the genetic information that encode the necessary tools for protein synthesis or generation of metabolic energy; hence they rely on their host to replicate and multiply. Using the host cell's machinery the virus generates copies of its genome and produces new viruses for the survival of its kind and the infection of new hosts.The viral replication process varies depending on the virus's genome. In 1971 David Baltimore, a Nobel Prize-winning biologist, created a system called Baltimore Classification System.According to this system, viruses are classified into seven classes based on their replication strategy: Regardless of the differences among viral species, they all share six basic replication stages: Attachment is the cycle's starting point and consists of specific bindings between anti-receptors (or virus-attachment proteins) and cellular receptors molecules such as (glyco)proteins. The host range of a virus is determined by the specificity of the binding. The attachment causes the viral protein to change its configuration and thus fuse with the host's cell membrane; thereby enabling the virus to enter the cell. Penetration of virus happens either through membrane fusion or receptor-mediated endocytosis and leads to viral entry. Due to their rigid cellulose-made (chitin in case of fungal cells) cell walls, plants and fungal cells get infected differently than animal cells. Often, a cell wall trauma is required for the virus to enter the cell. Uncoating is the removal of viral capsid, which makes the viral nucleic acids available for transcription. The capsid could have been degraded by either host or viral enzymes, releasing the viral genome into the cell. Replication is the multiplication of virus's genetic material. The process includes the transcription of mRNA, synthesis, and assembly of viral proteins and is regulated by protein expression.