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Related Concept Videos

What are Viruses?00:50

What are Viruses?

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Viral Mutations00:36

Viral Mutations

A mutation is a change in the sequence of bases of DNA or RNA in a genome. Some mutations occur during replication of the genome due to errors made by the polymerase enzymes that replicate DNA or RNA. Unlike DNA polymerase, RNA polymerase is prone to errors because it is not capable of “proofreading” its work. Viruses with RNA-based genomes, like HIV, therefore accrue mutations faster than viruses with DNA-based genomes. Because mutation and recombination provide the raw material for adaptive...
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Viruses are unique biological entities that blur the boundary between living and non-living systems. Although they lack cellular structure and metabolic processes, they can exhibit characteristics of life when infecting a host. Their defining feature is a nucleic acid core, composed of either DNA or RNA, encapsulated within a protein coat called a capsid. This simple structure allows them to invade host cells and use their machinery for replication efficiently.Viral Structure and...
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Viruses are extraordinarily diverse in shape and size, but they all have several structural features in common. All viruses have a core that contains a DNA- or RNA-based genome. The core is surrounded by a protective coat of proteins called the capsid. The capsid is composed of subunits called capsomeres. The capsid and genome-containing core are together known as the nucleocapsid.
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Viruses with RNA Genomes

RNA viruses are categorized into positive-strand, negative-strand, or double-stranded groups based on their genomic structure and replication mechanisms. This classification dictates how they exploit host cellular machinery for protein synthesis and replication. Some RNA viruses also utilize reverse transcription as part of their life cycle, further diversifying their replication strategies.Positive-Strand RNA VirusesPositive-strand RNA viruses have genomes that function directly as messenger...
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Redefining viruses: lessons from Mimivirus.

Didier Raoult1, Patrick Forterre

  • 1Unité des Rickettsies, IRD-CNRS UMR 6236, IFR-48, Faculté de Médecine, 27 Bd Jean Moulin, 13385 Marseille, France. didier.raoult@gmail.com

Nature Reviews. Microbiology
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Summary
This summary is machine-generated.

This study proposes a new classification for biological entities, dividing them into ribosome-encoding and capsid-encoding organisms. This framework offers a positive definition for viruses based on their biological characteristics and life cycle.

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Area of Science:

  • * Proposes a novel biological classification system.
  • * Categorizes life into ribosome-encoding and capsid-encoding organisms.

Background:

  • * Addresses the limitations of defining viruses using negative criteria.
  • * Highlights the significant evolutionary role of viruses.

Approach:

  • * Introduces a new classification system for biological entities.
  • * Defines viruses as capsid-encoding organisms.
  • * Classifies other replicons as 'orphan replicons'.

Key Points:

  • * Establishes two primary organism groups: ribosome-encoding (eukaryotes, archaea, bacteria) and capsid-encoding (viruses).
  • * Defines viruses by their protein and nucleic acid composition, self-assembly into nucleocapsids, and reliance on host ribosomes.
  • * Introduces 'orphan replicons' for entities like plasmids and viroids.

Conclusions:

  • * Offers a positive, criteria-based definition for viruses.
  • * Provides a new framework for understanding biological diversity and viral evolution.
  • * Reclassifies viruses based on their unique biological attributes and life cycle dependency.