Question

Viroids differ from viruses in:
A. Satellite RNA packaged with viral genome
B. Naked DNA molecules
C. Naked RNA molecules only
D. Naked DNA packaged with viral genome

Answer 1

The difference between virus and viroids exist in the biomolecules they contain. Viroids possess nucleic acid that is most commonly capable of forming secondary structures and also they are devoid of proteins.

Complete answer:
Nucleic acid (DNA or RNA) and a protein coat encapsulate the whole nucleic acid found in a virus. On the other hand, Viroid consists of a short circular, single-stranded RNA strand without protein coating.

Viroids are pathogens of plants: small spherical, single-strand RNA particles that are much simpler than a virus. They have neither a capsid nor an external shell, but like viruses, they can only replicate in host cells. However, Viroids do not contain proteins. They only contain one RNA molecule.

Therefore, viruses have their nucleic acid (DNA or RNA) packaged inside the capsid whereas viroids don’t contain DNA, rather they have RNA which is not packaged inside a protein coat.

Hence, The correct answer is option (C).

Additional information:
- Viruses are believed to infect plants and animals while viroids are known to infect plants only. Viruses may have RNA or DNA and are compulsory host cell translation machinery intracellular parasites.
- Viroids can only multiply within the host cell and require host DNA-dependent RNA polymerase for their replication. Viral genomes are encapsulated in a protein coat outside the host cells.
- Infectious particles are also called virions. Some virions have an outer lipid layer derived from host cells. Virions have surface receptor molecules that enable their attachment to and entry into host cells.
- A Viroid is made up of a single stranded circular RNA molecule that is much smaller and simpler than a virus. Viroids are pure RNA with no protein or lipid covering. Viroid genomes do not encode any proteins, as compared to viral genomes.

Note: Viroid is smaller relative to viruses. Its effectiveness is confined solely to plants. They contain a single stranded RNA genome that is not capable of encoding proteins. Viruses can have either RNA or DNA molecules which are enclosed in a protein coat. Viroids cause infections in higher plants.