Viruses nucleic acid replication/translation

Replication of Viral Nucleic Acid. In addition to producing molecules for the formation of new capsids, the virus must replicate its nucleic acid to provide genetic material for packaging into the capsids. The way in which this is done might vary. In positive-sense, single-strand RNA viruses, a polymerase translated from viral mRNA produces negative-sense RNA from the positive-sense template which is then repeatedly transcribed into more positive strands. 

Viruses are usually not considered as hving entities because they are not able to replace their parts or carry out metabohsm on their own. They are very small in size, ranging from tens to hundreds of nanometers. They can be replicated only when they are in association with a living cell (host). The host translates the genetic information present in the virus, which lead to its replication. The consequence of this rephcation to the hving host is either disease or death. The viruses have very simple genetic elements that consist of nucleic acid surrounded by protein and other substances (3,9). 

The way in which the viral genome is replicated depends entirely on the nature of the nucleic acid carried by the virus. Positive strand RNA viruses (e.g. poliovirus) can use the parent RNA directly as mRNA, after the acquisition from the host cell of a terminal sequence enabling immediate translation. With negative strand RNA viruses (e.g. influenza virus), a positive RNA strand complementary in base sequence to the parent RNA has to be transcribed using an RNA-dependent RNA polymerase carried by the virus, as eukaryotic cells do not possess such enzymes. 

Chapter 17, which focuses on the structure of the nucleic acids, begins with a description of DNA structure and the investigations that led to its discovery. This is followed by a discussion of current knowledge of genome and chromosome structure, as well as the structure and roles of the several forms of RNA. Chapter 17 ends with the description of viruses, macromolecular complexes composed of nucleic acid and proteins that are cellular parasites. In the following chapter (Chapter 18), several aspects of nucleic acid synthesis and function (i.e., DNA replication and transcription) are discussed. Protein synthesis (translation) is described in Chapter 19. 

Viruses are simple genes, made up of RNA or DNA, that infect cells and take over their replication, transcription, and translation machinery. Viruses are characterized by their structure, their type of nucleic acid, whether it is single- or double-stranded, and their mode of infection. Viruses are known to cause many diseases, and they may be very specific to a particular species and cell type. 

The study of bacterial viruses has provided many of the most important breakthroughs in modern biology. Thus, the role of nucleic acids in heredity and the basic mechanisms of mutation, replication, transcription and translation of the genetic material were mainly revealed through the use of bacteriophages. 

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