Question: Are viral genomes consistent across all viruses?

Viruses come in many shapes and sizes, but these features are consistent for each viral family. As we have seen, all virions have a nucleic acid genome covered by a protective capsid.

How do viral genomes differ among viruses?

The vast majority of viruses have RNA genomes. Plant viruses tend to have single-stranded RNA genomes and bacteriophages tend to have double-stranded DNA genomes. Viral genomes are circular, as in the polyomaviruses, or linear, as in the adenoviruses. The type of nucleic acid is irrelevant to the shape of the genome.

Are viral genomes Polycistronic?

In contrast to double-stranded RNA viruses, single-stranded viruses contain a single polycistronic RNA genome. Upon infection, the RNA genome may serve as mRNA and may be translated directly into a single polypeptide that is cleaved to individual proteins by cytoplasmic proteases.

Do viruses have different genomes?

Currently, over 4000 viruses have been described, classified into 71 families. Even though viruses possess small genomes, they exhibit enormous diversity compared with plants, animals and even bacteria. With respect to the genome, viruses are broadly divided into DNA viruses and RNA viruses.

Are viral genomes unstable?

DNA viruses usually show greater genome stability than RNA viruses. However, recent genome-wide molecular evolution and experimental studies have shown that DNA viruses can exhibit rapid sequence changes that are often found in loci involved in dynamic host–virus interactions.

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How are proteins encoded in viral RNA genomes?

RdRp is a nonstructural protein, meaning that it is not found within the assembled virion. Instead it is translated directly from the infecting genome shortly after penetration. RdRp and other viral proteins needed for viral RNA synthesis are encoded as a polyprotein that is cleaved by virally encoded proteases.

Why do viruses mutate so much?

Antigenic Drift

As a virus replicates, its genes undergo random “copying errors” (i.e. genetic mutations). Over time, these genetic copying errors can, among other changes to the virus, lead to alterations in the virus’ surface proteins or antigens.

Is it normal for a virus to mutate so quickly?

All viruses change but not always at the same rate. “The rate of change varies from virus to virus. Some change very fast, such as the influenza virus. That is why we get a new flu vaccine every year.

What viruses are RNA viruses?

1.1. RNA Viruses. Human diseases causing RNA viruses include Orthomyxoviruses, Hepatitis C Virus (HCV), Ebola disease, SARS, influenza, polio measles and retrovirus including adult Human T-cell lymphotropic virus type 1 (HTLV-1) and human immunodeficiency virus (HIV).

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