Question

Viroids have a
A) ds RNA enclosed by a protein coat
B) ds DNA not enclosed by a protein coat
C) ss RNA enclosed by a protein coat
D) ss RNA not enclosed by a protein coat

Answer 1

Hint:The first viroid was discovered from potato spindle tuber disease during the year of 1970 by Theodor Otto Diener who was a plant pathologist at the US Department of Agriculture’s Research Center which is located in Beltsville, Maryland.

Complete answer:
Viroids are typically composed of short circular single stranded RNA that lacks protein coat. Although viroids are known to contain nucleic acid but they do not encode any proteins. The viroid uses host cell
RNA Polymerase II which normally is involved in the formation of mRNA from the DNA, to replicate its genome through the rolling circle mode of replication.
Few of the properties of viroids makes them more plausible macromolecules than any existing RNA components or even introns, these are- they have high percentage of guanine and cytosine which not only increases their stability but also replication fidelity., their circular structure which ensures complete genome replication without the help of any tags, small size and structural periodicity that helps them to assemble on to large genomes.

Hence the correct answer is option (D) ssRNA not enclosed by a protein coat.

Note:Viroids are well known in their roles of causing plant diseases, recent research have shown that viroids are capable of causing infections in plants by means of RNA silencing. The viroid siRNA is capable of base pairing with the mRNA of the plant that leads to the mRNA degradation or inhibition of translation into proteins.