Test: Viroids, Prions and Lichens - NEET MCQ

The term used to describe infectious agents consisting of abnormally folded proteins, similar in size to viruses, is "prions."

• These agents are responsible for diseases like mad cow disease (BSE) and Creutzfeldt-Jakob disease (CJD) in humans.

To solve the matching problem, let's align each item from Column-I with its corresponding description in Column-II:

1. Saprophyte: This term refers to organisms that decompose dead organic materials.

   • Match: (a) → (ii)

2. Parasite: This term describes organisms that live on living plants or animals.

   • Match: (b) → (iii)

3. Lichens: Lichens are a symbiotic association between algae and fungi.

   • Match: (c) → (iv)

4. Mycorrhiza: This is a symbiotic association of fungi with plant roots.

   • Match: (d) → (i)

So, the correct matching is:

• (a) → (ii)
• (b) → (iii)
• (c) → (iv)
• (d) → (i)

Therefore, the correct answer from the options provided is:

Option 1: (a) (ii), (b) (iii), (c) (iv), (d) (i)

Viroids : In 1971, T.O. Diener discovered a new infectious agent that was smaller than viruses and caused potato spindle tuber disease. It was found to be a free RNA; it lacked the protein coat that is found in viruses, hence the name viroid. The RNA of the viroid was of low molecular weight.

Statement (D) in incorrect as Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner.

Bacterial viruses or bacteriophages (viruses that infect the bacteria) are usually double stranded DNA viruses

Bovine spongiform encephalopathy, commonly called mad cow disease, as a notable disease caused by prions in cattle.

• Lichens are symbiotic associations between algae (phycobiont) and fungi (mycobiont).
• Algae prepare food for fungi, and fungi provide shelter and absorb mineral nutrients and water for their algal partners.

To determine the incorrectly paired item:
- A: Inert Crystals - Virus
- B: Free RNA - Viroids
- C: Normal protein - Prions
- D: Symbionts - Lichen

The incorrect pairing is: (C)

Prions are folded proteins not normal proteins
 

Potato spindle tuber disease is caused by an infectious agent called viroid. Viroids comprise free RNA of low molecular weight. They lack a protein coat that is found in viruses .

Nucleocapsid are viruses .Viruses are crystalline structures as they have a nucleic acid enclosed with a protein coat.

T.O. Diener discovered a new infectious agent in 1971 that was smaller than viruses and caused potato spindle tuber disease. This agent was identified as a viroid, which is a type of infectious entity that consists of a short strand of RNA without a protein coat.

(B) The correct answer is B:  Body of lichens is made up of phycobionts only.
: Lichens are symbiotic associations i.e. mutually useful associations, between algae and fungi. The algal component is known as phycobiont and the fungal component as mycobiont, which are autotrophic and heterotrophic, respectively. Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner. So close is their association that if one saw a lichen in nature one would never imagine that they had two different organisms within them. Lichens are very good pollution indicators – they do not grow in polluted areas.

. In plants diseases caused by virus include, the symptoms can be mosaic formation, leaf rolling and curling, yellowing and vein clearing, dwarfing and stunted growth.

The correct answer is: d) Prions are smaller in size than viruses.

• Viroids are actually smaller than viruses and consist solely of a short strand of circular RNA without a protein coat. They are even simpler than viruses.
• Prions are infectious protein particles without any nucleic acid, making them smaller and structurally simpler than viruses.
• Lichens are a mutualistic symbiotic association between a fungus and an alga (or cyanobacterium).
• In mutualism, both organisms benefit and are dependent on each other, which contradicts option 3 about proto-cooperation.

T.O. Diener discovered a new infectious agent smaller than viruses, causing the potato spindle tuber disease, identifying this agent as a viroid.

Viroids are the smallest infectious pathogens known. They are composed solely of a short strand of circular, single-stranded RNA that has no protein coating.