How do ssRNA viruses replicate their genome?

DNA viruses replicate their genomes using DNA polymerase enzymes and transcribe their mRNA using DNA-dependent RNA polymerase enzymes. Both (+) and (−) ssRNA viruses replicate and transcribe their genomes using RdRp enzymes (Fig. 3.1).

How might RNA based genome result in an increased infection rate?

RNA viruses have higher probabilities to infect new host species because of their exceptionally shorter generation times and their faster evolutionary rates. The rapid evolutionary rates of RNA viruses build from frequent error-prone replication cycles (Holmes 2009).

Why is a segmented genome good for a virus?

A segmented genome enables the virus to generate reassortants. In this process, the RNA molecules of different virus strains are mixed or reshuffled in doubly infected cells during replication and morphogenesis. In this way, progeny viruses can obtain new combinations of RNA segments and thus gain novel properties.

Why do RNA viruses appear to have a higher rate of mutation?

The higher per-site mutation rates of RNA viruses can be explained in part by the RNA-dependent RNA polymerases (RdRp) that replicate their genomes. Unlike many DNA polymerases, RdRp do not have proofreading activity and are thus unable to correct mistakes during replication.

Why do RNA viruses need to encode their own polymerase?

Viruses first need to convert their genomes into mRNA that can be translated into viral proteins. Viruses that spend their entire life cycle in the cytoplasm do not have access to host polymerases and thus need to encode their own polymerases for transcription and replication.

How do viral genomes replicate?

During attachment and penetration, the virus attaches itself to a host cell and injects its genetic material into it. During uncoating, replication, and assembly, the viral DNA or RNA incorporates itself into the host cell’s genetic material and induces it to replicate the viral genome.

Do RNA viruses mutate more than DNA viruses?

RNA viruses mutate faster than DNA viruses, single-stranded viruses mutate faster than double-strand virus, and genome size appears to correlate negatively with mutation rate.

What is a human infecting virus that has a DNA based genome?

Most of these viral genes come from retroviruses, RNA viruses that insert DNA copies of their own genes into our genomes when they infect cells. HHV-6 is unique because it is the only known human DNA herpesvirus that integrates into the human genome and can be routinely inherited.

Do viruses have segmented genomes?

With respect to the genome, viruses are broadly divided into DNA viruses and RNA viruses. Both DNA and RNA viruses can either single stranded or double stranded, with a circular, linear or segmented arrangement. DNA and RNA viruses are distinguished by their features, such as monopartite or multipartite.

What is a segmented genome virus?

Segmented RNA viruses. Viruses in which the genome consists of more than one RNA molecule (that is, segments). The genome segments can be packaged within a single virion particle or into separate particles.

Why do RNA viruses encode their own RNA dependent RNA polymerase and package them in viral particles?

12.1. Viruses first need to convert their genomes into mRNA that can be translated into viral proteins. Viruses that spend their entire life cycle in the cytoplasm do not have access to host polymerases and thus need to encode their own polymerases for transcription and replication.