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Bacteria, Viruses, and Protists

Virus Basics

Where did viruses originate?

The most widely accepted hypothesis is that viruses are bits of nucleic acid that “escaped” from cells. According to this view, some viruses trace their origin to animal cells, some to plant cells, and others to bacterial cells. The variety of origins may explain why viruses are species-specific—that is, why some viruses only infect species that they are closely related to or the organisms from which they originated. This hypothesis is supported by the genetic similarity between a virus and its host cell.



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