Which of the following bacterial structures is responsible for antibiotic resistance through enzymatic inactivation?
Answer: A
Plasmids are extrachromosomal DNA that carry antibiotic resistance genes and can be transferred between bacteria, making them primary vectors for resistance.
Q.22Easy
What is the primary mode of transmission for Hepatitis A virus in developing countries?
Answer: A
HAV is transmitted through fecal-oral route, particularly in areas with poor sanitation and hygiene practices.
Q.23Easy
Which bacterial species is most commonly associated with food poisoning from poultry products?
Answer: A
Salmonella typhimurium is a major cause of foodborne illness from poultry, causing acute gastroenteritis.
Q.24Easy
Which viral envelope protein is primarily responsible for binding to host cell receptors in influenza virus?
Answer: A
Hemagglutinin (H protein) binds to sialic acid receptors on host cells, initiating viral entry in influenza.
Q.25Easy
In bacterial DNA replication, which enzyme unwinds the double helix?
Answer: A
DNA helicase breaks hydrogen bonds between base pairs to unwind the DNA double helix during replication.
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Q.26Easy
Which of the following viruses has been successfully eradicated from the wild through vaccination programs?
Answer: A
Smallpox was declared eradicated in 1980 following intensive global vaccination campaigns, the only human virus to achieve this status.
Q.27Easy
Which of the following bacterial structures is responsible for adherence to host cells?
Answer: A
Pili and fimbriae are hair-like appendages that facilitate bacterial adhesion to host cells and surfaces, essential for pathogenesis.
Q.28Easy
Gram-positive bacteria retain crystal violet dye due to:
Answer: D
The thick peptidoglycan layer in gram-positive bacteria traps the crystal violet-iodine complex, and absence of LPS distinguishes them from gram-negative bacteria.
Q.29Easy
Which viral structure is essential for cell recognition and attachment?
Answer: B
Spike proteins on viral surfaces recognize and bind to specific receptors on host cells, determining viral tropism and infectivity.
Q.30Easy
Endospores in bacteria are primarily formed for:
Answer: B
Endospores are dormant structures that allow bacteria like Bacillus and Clostridium to survive extreme temperatures, desiccation, and chemical stress.
Q.31Easy
Which of the following is a DNA virus?
Answer: C
Varicella-zoster virus (VZV) is a double-stranded DNA virus belonging to the Herpesviridae family, causing chickenpox and shingles.
