What is Virus?
A virus is an infectious parasite that can reproduce by itself in living cells of bacteria, plants and animals, whose name originates from a latin word that means poison or slimy liquid. Once a susceptible cell is infected, a virus can start the cell machinery to generate more viruses. Many viruses have either DNA or RNA as a genetic element. The nucleic acid can have single or double strands. The whole infectious virus, called as virion has nucleic acid and an outer shell of protein. The most simple virus includes only enough DNA or RNA for encoding four proteins and the most complex encodes 100-200 proteins.
Classification of Viruses
Viruses are classified based on the chemical composition, size and shape, genome structure and modes of replication. Helical morphology is found in nucleocapsids of different pleomorphic and filamentous viruses. Helical nucleocapsids includes a helical array of capsid proteins coated over a filament of nucleic acid. Many capsomeres arrangement are effective in identification and many consists an outer envelope as well.
The whole genome may cover either one molecule of nucleic acid(monopartite genome) or different segments of nucleic acid (multipartite genome). The different kinds of genome call for various replication techniques.
Structure and Function
Viruses are tiny obligate intracellular, and contain either DNA or RNA genome and surrounded by a protective protein(consisting of virus) coating. It can be seen as genetic element and characterized by a combined evolution of virus and the host. Viruses mainly depend on host that deliver the complex metabolic machinery of prokaryotic or eukaryotic cells for propagation. The main task of virion is to carry its DNA or RNA genome to the host cell so that the genome can be transcribed by the host cell. The viral genome is packed in a capsulated symmetric protein. The protein associated with nucleic acid known as nucleoprotein produces the nucleocapsid with the genome.
Know more about and refer articles that describe the structure of viruses and general structure, refer Byju’s.