First Aid USMLE STEP 1: viruses
Practice Test Questions 2025-2026 All
Answered Correct.
Viral structure - general features schematic - Answer
Viral recombination - Answer Exchange of genes between 2 chromosomes by crossing over
within regions of significant base sequence homology.
Viral reassortment - Answer When viruses with segmented genomes (e.g., influenza virus)
exchange genetic material. For example, the 2009 novel H1N1 influenza A pandemic emerged
via complex viral reassortment of genes from human, swine, and avian viruses.
Has potential to cause antigenic shift.
Viral complementation - Answer -When 1 of 2 viruses that infect the cell has a mutation that
results in a nonfunctional protein. The nonmutated virus "complements" the mutated one by
making a functional protein that serves both viruses.
-For example, hepatitis D virus requires the presence of replicating hepatitis B virus to supply
HBsAg, the envelope protein for HDV.
Viral phenotypic mixing - Answer Occurs with simultaneous infection of a cell with 2 viruses.
Genome of virus A can be partially or completely coated (forming pseudovirion) with the
surface proteins of virus B. Type B protein coat determines the tropism (infectivity) of the hybrid
virus. However, the progeny from this infection have a type A coat that is encoded by its type A
genetic material.
Live attenuated viral vaccines vs. killed/inactive vaccines - Answer Induce humoral and cell-
mediated immunity but have reverted to virulence on rare occasions.
Killed/inactivated vaccines induce only humoral immunity but are stable.
No booster needed for live attenuated vaccines.
Dangerous to give live vaccines to
,MMR = measles, mumps, rubella; live
attenuated vaccine that can be given to HIV+ patients who do not show signs of
immunodeficiency.
Viruses with live attenuated vaccine - Answer Smallpox, yellow fever, rotavirus, chickenpox
(VZV), Sabin polio virus, MMR, Influenza (intranasal).
Killed viral vaccines - Answer Rabies, Influenza (injected), Salk Polio, and HAV vaccines.
Killed/inactivated vaccines induce only humoral immunity but are stable.
Subunit viral vaccines - Answer HBV (antigen = HBsAg), HPV (types 6, 11, 16, and 18)
All DNA viruses except the _________ are dsDNA. - Answer Parvoviridae (SS and linear)
All DNA viruses are linear except __________, ___________, ___________. - Answer
Papilloma-, polyoma-, and hepadnaviruses (circular)
All RNA viruses except _________ are ssRNA - Answer Reoviridae (DS linear)
Positive-stranded RNA viruses - Answer I went to a retro (retrovirus) toga (togavirus) party,
where I drank flavored (flavivirus) Corona (coronavirus) and ate hippy (hepevirus) California
(calicivirus) pickles (picornavirus).
Naked viral genome infectivity - Answer -Purified nucleic acids of most dsDNA (except
poxviruses and HBV) and ⊕ strand ssRNA
(≈ mRNA) viruses are infectious.
-Naked nucleic acids of ⊝ strand ssRNA and dsRNA viruses are not infectious. They require
polymerases contained in the complete virion.
All DNA viruses replicate in the ___________ except _________ . - Answer Nucleus, poxvirus
(carries own DNA-dependent RNA polymerase)
All RNA viruses replicate in the _____________ except __________ and _____________. -
, Give PAPP smears and CPR to a naked Heppy (hippy).
DNA = PAPP; RNA = CPR and hepevirus.
Where does herpes viruses acquire their envelopes? What about the rest of the viruses? -
Answer Herpes gets its envelope from the nuclear membrane; the rest get their envelope
from the plasma membrane when exiting the cell
DNA viruses are the HHAPPPPy viruses - Answer Hepadna, Herpes, Adeno, Pox, Parvo,
Papilloma, Polyoma
All DNA viruses are icosahedral except for __________. - Answer Pox (complex)
Herpesviruses virology - Answer -DNA
-Enveloped
-DS and linear
Hepadnavirus virology - Answer -DNA
-Enveloped
-Partially DS and circular
HBV:
-Acute or chronic hepatitis
-Not a retrovirus but has reverse transcriptase
Adenovirus virology - Answer -DNA
-Naked
-DS and linear
-Febrile pharyngitis (see picture A)—sore throat
-Acute hemorrhagic cystitis
-Pneumonia
Practice Test Questions 2025-2026 All
Answered Correct.
Viral structure - general features schematic - Answer
Viral recombination - Answer Exchange of genes between 2 chromosomes by crossing over
within regions of significant base sequence homology.
Viral reassortment - Answer When viruses with segmented genomes (e.g., influenza virus)
exchange genetic material. For example, the 2009 novel H1N1 influenza A pandemic emerged
via complex viral reassortment of genes from human, swine, and avian viruses.
Has potential to cause antigenic shift.
Viral complementation - Answer -When 1 of 2 viruses that infect the cell has a mutation that
results in a nonfunctional protein. The nonmutated virus "complements" the mutated one by
making a functional protein that serves both viruses.
-For example, hepatitis D virus requires the presence of replicating hepatitis B virus to supply
HBsAg, the envelope protein for HDV.
Viral phenotypic mixing - Answer Occurs with simultaneous infection of a cell with 2 viruses.
Genome of virus A can be partially or completely coated (forming pseudovirion) with the
surface proteins of virus B. Type B protein coat determines the tropism (infectivity) of the hybrid
virus. However, the progeny from this infection have a type A coat that is encoded by its type A
genetic material.
Live attenuated viral vaccines vs. killed/inactive vaccines - Answer Induce humoral and cell-
mediated immunity but have reverted to virulence on rare occasions.
Killed/inactivated vaccines induce only humoral immunity but are stable.
No booster needed for live attenuated vaccines.
Dangerous to give live vaccines to
,MMR = measles, mumps, rubella; live
attenuated vaccine that can be given to HIV+ patients who do not show signs of
immunodeficiency.
Viruses with live attenuated vaccine - Answer Smallpox, yellow fever, rotavirus, chickenpox
(VZV), Sabin polio virus, MMR, Influenza (intranasal).
Killed viral vaccines - Answer Rabies, Influenza (injected), Salk Polio, and HAV vaccines.
Killed/inactivated vaccines induce only humoral immunity but are stable.
Subunit viral vaccines - Answer HBV (antigen = HBsAg), HPV (types 6, 11, 16, and 18)
All DNA viruses except the _________ are dsDNA. - Answer Parvoviridae (SS and linear)
All DNA viruses are linear except __________, ___________, ___________. - Answer
Papilloma-, polyoma-, and hepadnaviruses (circular)
All RNA viruses except _________ are ssRNA - Answer Reoviridae (DS linear)
Positive-stranded RNA viruses - Answer I went to a retro (retrovirus) toga (togavirus) party,
where I drank flavored (flavivirus) Corona (coronavirus) and ate hippy (hepevirus) California
(calicivirus) pickles (picornavirus).
Naked viral genome infectivity - Answer -Purified nucleic acids of most dsDNA (except
poxviruses and HBV) and ⊕ strand ssRNA
(≈ mRNA) viruses are infectious.
-Naked nucleic acids of ⊝ strand ssRNA and dsRNA viruses are not infectious. They require
polymerases contained in the complete virion.
All DNA viruses replicate in the ___________ except _________ . - Answer Nucleus, poxvirus
(carries own DNA-dependent RNA polymerase)
All RNA viruses replicate in the _____________ except __________ and _____________. -
, Give PAPP smears and CPR to a naked Heppy (hippy).
DNA = PAPP; RNA = CPR and hepevirus.
Where does herpes viruses acquire their envelopes? What about the rest of the viruses? -
Answer Herpes gets its envelope from the nuclear membrane; the rest get their envelope
from the plasma membrane when exiting the cell
DNA viruses are the HHAPPPPy viruses - Answer Hepadna, Herpes, Adeno, Pox, Parvo,
Papilloma, Polyoma
All DNA viruses are icosahedral except for __________. - Answer Pox (complex)
Herpesviruses virology - Answer -DNA
-Enveloped
-DS and linear
Hepadnavirus virology - Answer -DNA
-Enveloped
-Partially DS and circular
HBV:
-Acute or chronic hepatitis
-Not a retrovirus but has reverse transcriptase
Adenovirus virology - Answer -DNA
-Naked
-DS and linear
-Febrile pharyngitis (see picture A)—sore throat
-Acute hemorrhagic cystitis
-Pneumonia
