Question

Viroids have
A) Single stranded RNA not enclosed by protein coat
B) Single stranded DNA not enclosed by protein coat
C) Double stranded DNA enclosed by protein coat
D) Double stranded RNA enclosed by protein coat

Answer 1

Hint:Let us first understand what is meant by virus and viroids.Virus is a microscopic particle that contains only one nucleic acid either DNA or RNA along with capsid which is a protein coat. The plant pathogens that contain only single stranded RNA and do not enclose any proteins are called viroids.

Complete answer:
Viroids are much smaller compared to viruses and infects plants only.
These are the smallest agents known for causing infectious disease. They contain short, single stranded circular RNA without the protein coat. Unlike the normal cell, they do not have nucleus, mitochondria, ribosomes and some of them even lack cytoplasm. do not have the ability to replicate or reproduce outside the host cell.

Additional information: The first discovered viroid is PSTVd ( Potato spindle tuber viroid) known to infect the potato plant causing potato spindle tuber disease. In a plant cell, if replication of viroids occurs in the nucleus then it is called as Pospiviroidae ;if the replication of viroids occur in chloroplast then it is called as Avsunviroidae.

Therefore the correct answer is (a) Single stranded RNA not enclosed by protein coat.

Note:Viroids do not have the ability to replicate or reproduce outside the host cell as they do not contain cell organelles like nucleus, mitochondria etc unlike a normal cell.therefore they are non functional outside a host cell.