Question

T.O. Diener discovered a/an
(a)Capsid-free infectious RNA
(b)Capsid-free infection DNA
(c)Infectious protein
(d)Bacteriophage

Answer 1

Theodor Otto Diener is the Swiss-American plant pathologist who, in 1971, discovered that the causative agent of the potato spindle tuber disease isn't a virus.

Complete answer:
Theodor Otto Diener discovered a capsid free infection DNA, which is the causative agent of the potato spindle tuber disease. It was not a virus, but a completely unique agent, which consists solely of a brief strand of single-stranded RNA without a protein capsid.

Additional Information:
- Viroids are composed of the macromolecule, they are doing not code for any protein
- Viroids small size, imposed by error-prone replication.
- Their high guanine and cytosine content, which increases stability and replication fidelity.
- Their circular structure, which confirms complete replication without genomic labels.
- Existence of structural periodicity, which allows modular assembly into enlarged genomes.
- Their lack of protein-coding ability, according to a ribosome-free habitat.
-Replication regulated in some by ribozymes—the fingerprint of the RNA world. - Viroids are now commonly thought of as remnants from the "RNA world" since they are composed of the only RNA and have ribozyme activity.
So, the right answer is ‘Capsid-free infectious RNA’.

Note: All known viroids are inhabitants of higher plants, and most cause diseases, whose respective economic importance on humans vary widely. Viroids were originally thought to be either the evolutionary precursors or degenerate descendants of conventional viruses.