Question

We defined viruses as infectious particles composed of a nuclei acid genome enclosed in a protein coat. We also added, according to Andre Lwoff, that these particles must be potentially pathogenic. Why do you think this explanation must be included in criteria that such particles have to meet in order to be considered viruses.

Answer 1

Viruses are organisms that are obligate intracellular parasites. Viruses are mobile elements and require a specialized host cell for propagation. The host cells provide the cellular machinery for replication of the virus. The virus attached to the host cell, and then injects its nucleic material (DNA or RNA) into the cell. This nucleic acid integrates into the host cell genome and replicates. It synthesizes all the proteins required for replication and formation of new virions. Once new virions are produced, they will lyses the cell and are released. Hence, viruses are pathogenic as they force the host cell to allow their multiplication and in this process, the host cells will be damaged.

Viruses are composed of a capsule that houses the nucleic acids. The capsule is required for attaching to the host cell. The capsid is made up of basic proteins. The nucleic acid will be inserted into the cell and replicated. The nucleic acid contains all the genetic information required for successful formation of new viruses. The genes present on the nucleic acid will be transcribed and translated. Viruses are classified based on the capsid morphology and as well as the nucleic acids present and its mode of replication.

Organisms are therefore classified as viruses, only if they have a capsid surround the nucleic acid and are infectious and potentially pathogenic. This information is required to be included in the criteria for classification as viruses.