Viruses are tiny and smaller in its size, ranging between 30-50 nm. Viruses do not contain cells and usually lack a cell wall but are surrounded by a protective protein coating called the capsid. It can be seen as a genetic element and is characterized by the combined evolution of the virus and the host. They contain either RNA or DNA as the genetic material.
Viruses mainly depend on a host to deliver the complex metabolic machinery of prokaryotic or eukaryotic cells for propagation. The main task of the virus is to carry its DNA or RNA genome to the host cell, which then can be transcribed by the host cell. The viral genome structure is packed in a capsulated symmetric protein. The protein associated with nucleic acid (also known as nucleoprotein) produces the nucleocapsid with the genome.
Bacteriophage and HIV
These microbes belong to the family viridae and genus virus. Viruses could not be placed in any of the kingdoms because they are practically neither living nor dead. The term virus was coined by the Dutch microbiologist, Martinus Willem Beijerinck in the year 1897. It is derived from Latin, which means poison or venomous substance.
Once a susceptible cell is infected, a virus can start the cell machinery to generate more virus. Viruses are composed of a core of DNA or RNA surrounded by a protein coat. They are very small and their size ranges from 20 nanometers to 250 nanometers. Therefore, they can only be seen with an electron microscope
Many viruses have either DNA or RNA as the genetic element and the nucleic acid with single or double strands. The whole infectious virus, called as virion has nucleic acid and an outer shell of proteins. The simplest virus includes DNA or RNA for encoding four proteins and the most complex encodes 100-200 proteins.
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