A bacterial strain shows resistance to multiple antibiotics. Which genetic element is most likely responsible?

The correct answer is B: Plasmids carrying resistance genes. Plasmids are extra-chromosomal DNA elements that carry multiple antibiotic resistance genes and can be horizontally transferred between bacteria, leading to multi-drug resistance.

Which viral enzyme is critical for reverse transcription in retroviruses?

The correct answer is C: Reverse transcriptase. Reverse transcriptase synthesizes DNA from viral RNA, enabling retroviruses like HIV to establish infection by converting their genome for integration into host DNA.

Which bacterial species is an obligate intracellular pathogen that causes Q fever?

The correct answer is A: Coxiella burnetii. Coxiella burnetii is highly infectious, forms spores, and is transmitted through aerosol route from infected animals.

A patient presents with atypical pneumonia. Which bacterial pathogen should be considered if Gram staining shows no organism but PCR is positive?

The correct answer is A: Mycoplasma pneumoniae. Mycoplasma lacks a cell wall and does not stain with Gram staining but is detectable by PCR, causing atypical pneumonia.

Which of the following is a characteristic feature of SARS-CoV-2 that contributes to its high transmissibility?

The correct answer is A: Presence of spike protein with high receptor binding affinity. The spike protein of SARS-CoV-2 has high affinity for ACE2 receptors, enabling efficient cellular entry and transmission.

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Microbiology

Bacteria, viruses, immunology, genetics

22 Q 1 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–22 of 22

Topics in Microbiology

All Bacteria & Viruses 100

Q.21 Hard Bacteria & Viruses

Which of the following is a characteristic of prions that distinguishes them from viruses?

A They contain RNA

B They are entirely composed of protein with no nucleic acids

C They replicate by binary fission

D They have a cell membrane

Correct Answer: B. They are entirely composed of protein with no nucleic acids

EXPLANATION

Prions are infectious agents composed solely of misfolded proteins (PrPsc) without any nucleic acids. They cause diseases like Creutzfeldt-Jakob disease (CJD). Viruses require nucleic acids for replication.

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Q.22 Hard Bacteria & Viruses

What is the most probable reason for antibiotic resistance development in bacteria?

A Direct mutation from antibiotics

B Exposure to antibiotics selects for resistant strains

C Bacteria intentionally become resistant

D Antibiotics increase bacterial DNA copying

Correct Answer: B. Exposure to antibiotics selects for resistant strains

EXPLANATION

Antibiotic resistance develops through natural selection. When antibiotics kill susceptible bacteria, resistant strains (with pre-existing mutations or acquired resistance genes) survive and proliferate.

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