How Viruses Work: Virology

Viruses encode enzymes and follow unique pathways:

Approximately all viruses encode unique proteins and enzymes, in addition, they follow unique pathways to transfer their genetic data. This phenomenon is progressively pronounced in the case of RNA viruses, they either use RNA dependent RNA polymerase or in case of retrovirus (HIV) RNA dependent DNA polymerase is used to complete their replication cycle. Both of these procedure requires one of the unique enzymes that are encoded by the virus following infection to the host cells and are commonly absent somewhere else.

The RNA dependent RNA polymerase and reverse transcriptase have negligible proofreading capacity, subsequently, their error rate is very high (1 in 10,000) as compared to the DNA replication. This implies that an RNA virus particle will contain at least 1 from its parental wild type virus. The presence of wide range of subspecies of the virus particles in a population is also called a subspecies nature of RNA viruses. Because of this phenomenon, most of the RNA viruses have their genome size in the range of 5-15kb (coronavirus size is 30kb). In reverse cases of DNA viruses where proofreading and error repair activity ensures exact and accurate replication of the viral DNA as big as 800 kb. The fact that DNA is steadier chemically than RNA likely explains to us why all thermophilic hosts contain viruses that have dsDNA as their genetic material.