Question

T.O.Diener (1971) discovered a new infectious agent that was smaller than viruses.It was
A)Viruses
B)Viroids
C)Prions
D)Lichens

Answer 1

Hint: Farmers started to find a disease causing their potatoes to shrivel and become deformed around the time Theodor O. Diener was born in the early 1920s. Many plant pathologists believed a virus was to blame, unable to pin down the true cause of the disease.It wasn't until 50 years after the first mention of the disease that the true cause was discovered by Diener, who served in the Agriculture Department.

Complete answer:
Viroids are the smallest known contagious pathogens. They are composed solely of a circular, single-stranded RNA short strand that has no protein coating. All known viroids are inhabitants of higher plants, and most of them cause diseases that differ widely in their economic value to humans.

The viroid invades a cell, much like a virus, and hijacks its reproductive mechanisms. The cell is required to replicate the RNA of the viroid instead of its own. The viroid doesn't have DNA. RNA and DNA are nucleic acids, hereditary molecules; all genes are made of DNA, with the exception of viroids and some viruses.

The difference is that viroids do not have a protective protein coat between viroids and RNA viruses.

Viroid structure was first seen by electron microscopy directly, Viroids are small spherical, single stranded RNA molecules. They consist of a short stretch (a few hundred nucleobases) with a molecular weight between 1,07,000 and 1,27,000, of strongly complementary circular single stranded RNA without protein coat. The nucleotides of Viroid are 240 to 380 long, and all have dumb-bell structures

Hence, the correct answer is option (B)

Note: For any protein, Viroid RNA does not code for it. By recruiting host proteins, they replicate spontaneously and multiply throughout the plant. Three enzymatic activities for viroid replication are required: RNA pol. II, RNAse and ligase of RNA.