AP-Micro Virology: Structure, Replication, and Diagnosis 1 — Questions and Answers
Question 1: The Baltimore classification system categorizes viruses primarily based on:
- Host range and tissue tropism
- Genome type and the strategy used to produce mRNA (Correct answer)
- Capsid symmetry and size
- Mode of transmission and disease severity
Correct answer: Genome type and the strategy used to produce mRNA
The Baltimore system divides viruses into 7 classes based on their nucleic acid type (DNA/RNA, ss/ds, +/−) and how they generate mRNA for protein synthesis.
Question 2: Which of the following viruses is NON-enveloped (naked), making it more resistant to desiccation and detergents?
- Influenza virus
- HIV
- Adenovirus (Correct answer)
- Herpes simplex virus
Correct answer: Adenovirus
Adenovirus is a non-enveloped icosahedral virus; lacking a lipid envelope, it is resistant to drying, detergents, and many disinfectants.
Question 3: The repeating protein subunits that assemble to form the viral capsid are called:
- Envelopes
- Capsomeres (Correct answer)
- Peplomers
- Prions
Correct answer: Capsomeres
Capsomeres are the individual protein building blocks that polymerize to form the complete viral capsid surrounding the nucleic acid.
Question 4: Spike glycoproteins projecting from an enveloped virus surface are called:
- Capsomeres
- Nucleocapsids
- Peplomers (Correct answer)
- Teguments
Correct answer: Peplomers
Peplomers are the glycoprotein spikes on enveloped viruses (e.g., influenza HA and NA) that mediate receptor binding and immune recognition.
Question 5: Influenza hemagglutinin (HA) mediates which critical step in viral infection?
- Viral RNA replication in the nucleus
- Binding to sialic acid receptors on host respiratory cells (Correct answer)
- Budding of new virions from the cell surface
- Cleavage of sialic acid to release progeny virions
Correct answer: Binding to sialic acid receptors on host respiratory cells
Influenza HA binds sialic acid residues on host respiratory epithelial cells to initiate attachment and membrane fusion for viral entry.
Question 6: The unique enzyme present in retroviruses such as HIV that converts the RNA genome into DNA is:
- RNA-dependent RNA polymerase
- DNA-dependent DNA polymerase
- Reverse transcriptase (Correct answer)
- Integrase only
Correct answer: Reverse transcriptase
Reverse transcriptase (RNA-dependent DNA polymerase) copies the retroviral RNA genome into double-stranded DNA for integration into the host chromosome.
AP-Micro Virology: Structure, Replication, and Diagnosis 1
The Baltimore classification system categorizes viruses primarily based on: