Question

Which of the following is not true of viroids?

1) Viroids are small circular ssRNA molecules.
2) Viroids have no protein capsids.
3) Viroid RNA does not serve as mRNA nor does it direct the synthesis of mRNA.
4) Extracellular viroids have a lipid bilayer envelope.

Answer 1

The false statement about viroids is that they have an extracellular lipid bilayer envelope. Viroids consist of only circular single-stranded RNA, lack protein capsids or lipid envelopes, and do not code for any proteins.

Step-by-step explanation:

The statement that "Extracellular viroids have a lipid bilayer envelope" is not true of viroids. Viroids are simple plant pathogens that consist solely of a short strand of circular, single-stranded RNA without any protein capsids or lipid envelopes. They are much simpler than viruses and rely on the host cell machinery to replicate their RNA, but they do not manufacture proteins or have an extracellular form with a lipid bilayer envelope. Their RNA does not serve as mRNA, nor does it direct the synthesis of any proteins or mRNA.

Viroids are uniquely characterized by their small circular ssRNA molecules, lack of protein capsids, and the fact that their RNA does not function as mRNA. Additionally, unlike viruses, they do not have an outer envelope; this is an important distinction since viruses may possess a nucleic acid core surrounded by a protein capsid and sometimes an outer lipid envelope. Viroids are pathogenic to plants but no human diseases caused by viroids have been identified