Question

The smallest disease causing agent is
A.Virion
B.viroid
C.Prion
D.Mycoplasma

Answer 1

Hint:A variety of microorganisms can cause disease. Pathogenic organisms are of 5 main types: viruses, bacteria, fungi, protozoa, and worms. Pathogens are infectious agents that may cause sickness and disease in an exceeding number of various organisms, including humans. Viroids, which are considered disease causing pathogens because they are the smallest infectious.

Complete step by step answer:
-virion: A virion is a complete virus particle with a protein coat and nucleic acid core. A virion is an infectious form of the virus. The virion is surrounded by the protein coat and contains genetic material. It is a functional virus. It has the capacity to infect living tissue. Hence option A is incorrect.
-Viroid: Viroids are considered as the smallest infectious disease causing pathogens. The body of the viroid is the genetic material and it is composed of circular and single-stranded RNA which is The body is without any protein coat. The viroids are agents that cause infections commonly in the plants. Hence option B is correct.
-Prion: These are infectious pathogens. It does not contain nucleic acids. They are abnormally folded proteins found in some diseases such as scrapie. A prion is an abnormal form of a normally harmless protein found in the brain. It is responsible for a variety of fatal neurodegenerative diseases of animals including humans. Hence option C is incorrect.
-Mycoplasma: Mycoplasma is the smallest bacteria which does not possess a cell wall. It is a prokaryotic organism, composed of single-cell and non-motile. The cell membrane, proteins, DNA, and ribosomes are contained in the cell. The absence of a cell wall renders the organism as insensitive to most of the antibiotics. Hence option D is incorrect.
Hence, option B: viroid is the correct answer.

Note:Viroids are generally known as plant pathogens. They are small, single-stranded, RNA particles. They do not have a capsid or outer envelope of protein making them simpler than viruses, but like viruses, can reproduce only within a host cell. They do not have the capacity to make their own protein. They produce only a single, specific RNA molecule.