An Overview of Virus and Viroids ( Q & A)
CBSE Class 11 Biology - The Living World
Q1: Do five kingdom classification include viruses, viroids and lichens?
Answer: Five kingdom system of classification do not includes Virus, Viroids and Lichens.
Q2: What is a virus? What is its structure?
Answer: Viruses are non-cellular organisms having inert crystalline structure outside the living. A virus is a small particle consisting of a nucleic acid core surrounded by a protein coat; in order to reproduce, a virus must infect a living cell.
Q3: Name the botanist who discovered first that virus causes diseases.
Answer: In 1892, D.J.Ivanowsky recognized certain microbes as causal organism of mosaic disease of tobacco. Later in 1898, Martinus Beijerinck, a Dutch microbiologist, provided evidence that the agent that caused tobacco mosaic disease had many characteristics of a living organism. He named the causative agent as virus.
Q4: Do viruses contain genetic material?
Answer: Yes, In addition to proteins, viruses also contain genetic material that could be DNA or RNA. In general, virus that infect plants have single stranded RNA and virus that infect animals have double stranded DNA.
Q5: Name a few viral diseases.
Answer: Viruses infect the cells of all kinds of organisms; they cause serious diseases in plants and animals. Some common diseases caused by virus are common cold, influenza, AIDS, small pox, SARS, COVID19, leaf rolling and curling.
Q6: What is caspid?
Answer: The protein coat called capsid is made of small subunits called capsomeres, protects the nucleic acid. These capsomeres are arranged in helical or polyhedral geometric forms.
Q7: What are bacteriophage?
Answer: Bacteria-eaters or bacteria feeding virus are called Bacteriophage.They are usually double stranded DNA viruses.
Q8: How do viruses enter animal cells?
Answer: Viruses enter animal cells by membrane fusion or by endocytosis.
Q9: What are retroviruses? Give an example.
Answer: Retroviruses are RNA viruses that have a DNA polymerase called reverse transcriptase. It transcribes the RNA strands into into a DNA intermediate. This intermediate DNS gets attached to the host DNA. For example AIDS virus is a retrovirus type.
Q10: What are viroids and prions?
Answer: Viroids and prions are subviral agents and are much smaller in size than that of virus. Viroids are free RNA without protein coat. Prions are protein based infectious agents.
Q11: Who discovered viroids?
Answer: Viroids are discovered by T.O.Diener as new infectious agent smaller than virus causing potato spindle tuber disease.
Q12: Who discovered prions?
Answer: Prusiner, for discovering prions he was awarded Nobel prize in 1997.
👉See Also:
HIV/AIDS (A Brief Introduction)
The Living World (NCERT Chapter Solutions)
The Living World (AIPMT 7 MCQs)
The Living World (Taxonomical Aids)
The Living World VSQA
Biological Classification (NCERT Chapter Q & A)
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