Viroids are described as short circular ssRNA with no protein coating.

Are there any analogous infectious particles that contain DNA instead of RNA?

If DNA viroids do not exist, is there an obvious reason for this?


The definition on the Wikipedia page you recite uses the language 'no protein coating' as opposed to 'protein coating'.

A protein coating would make it a virus.

No protein-coating would make it a Viroid.

As far as we know DNA Viroids do not exist. But this is an advancing field of research and it depends on what structure of genetic material you are referring too.

The general different types of genetic material include - but are not limited to: Single-stranded DNA (ssDNA), Double-stranded DNA (dsDNA), Single-stranded RNA (ssRNA), and double-stranded RNA (dsRNA).

There is more information on Classes I and II DNA viruses here: https://www.ncbi.nlm.nih.gov/books/NBK21523/

If there were no DNA viruses without a protein coating - what is the reason? Viroids only infect plant cells. It may be that Viroids route of entry via microscopic junctions between plant cells (Plasmodesmata) are only large enough to fit single stranded genetic material. Therefore allowing ssDNA and ssRNA, but not dsDNA and dsRNA to act as plant cell infectious agents.

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    $\begingroup$ Welcome to SE Biology. I think, as a non-native speaker, you are on shaky ground criticizing the use of the word "particle" by the poster. The definition from Oxford Languages is "a minute portion of matter", which in no way implies a container. I would delete your first two paragraphs. Also questionable is your remark "it depends what you mean by DNA". DNA is unambiguous. The strandedness and cicularity of DNA may vary, but it is all DNA, and it is clear that the poster wishes to know whether an entity composed only of DNA with no associated protein can exist as an infectious agent. $\endgroup$
    – David
    Jul 16 '20 at 12:27
  • $\begingroup$ @David thank you for your response. I made your changes. I hope we can get on in the future here at SE. $\endgroup$
    – Andrew
    Jul 26 '20 at 0:34

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