Although viroids are composed of nucleic acid, they do not code for any protein. The viroid's replication mechanism uses RNA polymerase II, a host cell enzyme normally associated with synthesis of messenger RNA from DNA, which instead catalyzes "rolling circle" synthesis of new RNA using the viroid's RNA as a template.

Are viroids DNA or RNA?

Viroids are the smallest pathogenic agents yet described. They are single-stranded circular RNA molecules which vary in length from 246 to 463 nucleotides and are found only in plants.

Do viroids only have RNA?

Viroids are infectious agents that consist only of naked RNA without any protective layer such as a protein coat. Viroids infect plants (but no other forms of life) and are replicated at the expense of the host cell. Viroid genomes are small single-stranded circles of RNA that are only 250–400 bases long.