Question 1

Which of the following best describes an attenuated vaccine?

Accepted Answer

A vaccine containing live, weakened microorganisms that can replicate but do not cause disease

Question 2

Why is vaccination often the only feasible way to control most viral diseases?

Accepted Answer

Viruses replicate inside host cells, making them inaccessible to many drugs, so prevention by vaccination is more effective

Question 3

Which of the following statements about the oral (Sabin) and injected (Salk) polio vaccines is correct?

Accepted Answer

The Sabin vaccine can sometimes cause polio because it contains live attenuated virus that can revert to virulence

Question 4

A diagnostic test has a sensitivity of 95% and a specificity of 90%. What does this mean?

Accepted Answer

The test will correctly identify 95% of people with the disease and 90% of people without the disease

Question 5

Which of the following best explains why monoclonal antibodies are advantageous over conventional antibody production?

Accepted Answer

They are identical and specific to a single epitope, allowing for consistent and targeted diagnostic or therapeutic use

Question 6

Which of the following tests detects soluble antigens by forming a visible line of precipitation?

Accepted Answer

Precipitation test

Question 7

A patient receives a kidney transplant from a genetically unrelated donor. Which immune cells are primarily responsible for the rejection of this allograft?

Accepted Answer

Cytotoxic T lymphocytes recognizing nonself MHC antigens

Question 8

Which of the following is the most common mechanism by which bacteria develop resistance to penicillin?

Accepted Answer

Production of beta-lactamase enzymes that hydrolyze the beta-lactam ring

Question 9

Why do sulfa drugs selectively inhibit bacterial growth without harming human cells?

Accepted Answer

Humans obtain folic acid from their diet, while bacteria must synthesize it from PABA

Question 10

A patient is diagnosed with meningitis. Which body fluid is most commonly sampled to confirm the diagnosis?

Accepted Answer

Cerebrospinal fluid

Question 11

Which of the following best explains why the lower respiratory tract is nearly sterile under normal conditions?

Accepted Answer

Continuous movement of cilia and the mucociliary escalator

Question 12

Which group of antibiotics interferes with the DNA-replicating enzyme DNA topoisomerase?

Accepted Answer

Quinolones

Question 13

A patient with type O+ blood receives a transfusion of type A+ blood. What is the most likely immediate consequence?

Accepted Answer

Hemolytic transfusion reaction due to anti-A antibodies in the recipient's plasma

Question 14

Which of the following is a real-world example of a prophylactic cancer vaccine currently in use?

Accepted Answer

Hepatitis B vaccine to prevent liver cancer

Question 15

Which of the following best describes the mechanism of action of aminoglycoside antibiotics?

Accepted Answer

Inhibition of protein synthesis by binding to the 30S ribosomal subunit

Question 16

A patient is exposed to rabies virus and receives postexposure vaccination. Why is this approach effective?

Accepted Answer

The incubation period of rabies is long enough to allow the immune system to respond to the vaccine before symptoms develop

Question 17

Which of the following is the primary receptor on host cells to which HIV attaches?

Accepted Answer

CD4

Question 18

Which of the following best explains why antibiotics that target bacterial cell wall synthesis do not affect mammalian cells?

Accepted Answer

Mammalian cells lack peptidoglycan cell walls

Question 19

A patient is diagnosed with a fungal infection. Which sterol in the fungal cell membrane is the most common target for antifungal drugs?

Accepted Answer

Ergosterol

Question 20

Which of the following best describes the mechanism of immune complex (Type III) hypersensitivity reactions?

Accepted Answer

Soluble antigen-antibody complexes deposit in tissues, triggering inflammation

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