Q50. Which illness is not caused by a virus?
[SSC CHSL 2020 cycle, 11 August 2021]
(A) Leprosy
(B) Measles
(C) Smallpox
(D) Rabies
Answer: (A) Leprosy
Explanation: Leprosy is caused by Mycobacterium leprae, a bacterium affecting skin and peripheral nerves. Measles, smallpox and rabies arise from distinct viruses. Their prevention and treatment differ, highlighting why memorising the organism behind each disease remains important.
Q49. Which combination lists only diseases caused by coronaviruses?
[MPPSC Prelims 2020]
(A) SARS, MERS and COVID-19
(B) Malaria, dengue and influenza
(C) Typhoid, polio and rabies
(D) Hepatitis B, mumps and measles
Answer: (A) SARS, MERS and COVID-19
Explanation: SARS, MERS and COVID-19 are caused by different coronaviruses. Severe acute respiratory syndrome and Middle East respiratory syndrome involve related but distinct agents from SARS-CoV-2. The coronavirus family also includes pathogens causing some milder respiratory infections.
Q48. Why do usual antibacterial antibiotics not work directly against viruses?
[UPSC NDA (I) 2020]
(A) All viruses manufacture chlorophyll
(B) Viruses possess bacterial cell walls
(C) Viruses lack the bacterial metabolic targets of antibiotics
(D) Antibiotics always destroy antibodies
Answer: (C) Viruses lack the bacterial metabolic targets of antibiotics
Explanation: Antibiotics act on structures or pathways such as bacterial ribosomes, cell walls or enzymes. Viruses do not possess those bacterial targets and replicate using host cells. A bacterial complication of viral illness may still require antibiotic treatment when clinically indicated.
Q47. Which statement about hepatitis B and C is false?
[UPSC CSE Prelims 2019]
(A) Hepatitis B can spread through routes similar to HIV
(B) Hepatitis B has no vaccine whereas hepatitis C does
(C) Chronic infection may be asymptomatic for years
(D) Both viruses can cause long-term liver illness
Answer: (B) Hepatitis B has no vaccine whereas hepatitis C does
Explanation: An effective hepatitis B vaccine exists, while no hepatitis C vaccine is currently licensed. Both viruses can establish long-term infections and cause cirrhosis or liver cancer. Screening is important because symptoms may be absent during years of infection.
Q46. Which claim about viruses is wrong?
[UPSC NDA (II) 2019]
(A) They require living cells for replication
(B) They are obligate intracellular parasites
(C) They can photosynthesise to make food
(D) Outside a host they may be metabolically inactive
Answer: (C) They can photosynthesise to make food
Explanation: Viruses have no chloroplasts, independent energy metabolism or photosynthetic machinery. They reproduce only inside living host cells using host resources. Their extracellular particles can remain infectious without carrying out ordinary cellular processes such as growth or photosynthesis.
Q45. Rotavirus vaccination primarily prevents a severe form of which condition in children?
[SSC MTS, 7 August 2019]
(A) Diarrhoea
(B) Poliomyelitis
(C) Hepatitis B
(D) AIDS
Answer: (A) Diarrhoea
Explanation: Rotavirus is a major cause of gastroenteritis and severe dehydration in infants and young children. Rotavirus vaccines reduce severe diarrhoeal illness and hospitalisation. They do not prevent polio, viral hepatitis or HIV, which involve different pathogens.
Q44. Which plant condition is not generally caused by a virus?
[RPSC Senior Teacher Science 2019]
(A) Little-leaf disease of brinjal
(B) Yellow-vein mosaic of bhindi
(C) Banana bunchy top
(D) Papaya leaf curl
Answer: (A) Little-leaf disease of brinjal
Explanation: Little-leaf disease of brinjal is associated with phytoplasma, a wall-less bacterial pathogen. The other listed plant diseases are associated with viruses. This is an important distinction because plant infections may involve viruses, fungi, bacteria, phytoplasmas or viroids.
Q43. What best explains the relatively rapid genetic evolution of many RNA viruses?
[UPSC CDS (II) 2018]
(A) RNA genomes can be relatively error-prone during replication
(B) Viruses divide by binary fission
(C) Viruses photosynthesise
(D) Their genomes never undergo mutation
Answer: (A) RNA genomes can be relatively error-prone during replication
Explanation: Many RNA viruses replicate using polymerases with limited proofreading, allowing mutations to accumulate relatively quickly. Mutation rates differ among virus families; coronaviruses have some proofreading capability. Genetic variation may influence transmission, immunity, diagnostics and antiviral resistance.
Q42. Which genetic material is carried in HIV virions?
[UPSC NDA (I) 2018]
(A) Single-stranded circular DNA
(B) Double-stranded DNA
(C) Single-stranded RNA
(D) Double-stranded RNA
Answer: (C) Single-stranded RNA
Explanation: HIV is a retrovirus carrying two copies of single-stranded RNA. During infection it uses reverse transcriptase to generate a DNA copy that integrates into the host genome. This replication strategy distinguishes retroviruses from ordinary DNA viruses.
Q41. Who inaugurated the 2018 Pulse Polio campaign?
[RRB Group D, 19 September 2018]
(A) President Ram Nath Kovind
(B) Prime Minister Jawaharlal Nehru
(C) Vice-President B. D. Jatti
(D) President Rajendra Prasad
Answer: (A) President Ram Nath Kovind
Explanation: President Ram Nath Kovind launched the 2018 Pulse Polio campaign. The programme delivered oral polio vaccine to young children while maintaining vigilance against importation of poliovirus. Vaccination coverage remains important even after national elimination of endemic transmission.
